Raman spectroscopy experiments

Table XIII. Infrared and Raman Spectroscopy Experiments...

Hutchings et al. (118) carried out in situ Raman spectroscopy experiments with VPA precursors as they were being converted into the active catalyst. They foimd that during the activation there is a structural disordering at 370 °C, which corresponds to the appearance of MA in the catalytic reaction product. The disordering was foimd to occur at a lower temperature (300 °C) when MA was added to the butane/air reaction mixture. This result demonstrated that the presence of the products is important in controlling the structural transformations and that a highly disordered structure can be important in selective butane oxidation. 

Strength (FLS) empirical approach are discussed in Section 3 as methods for determining the molecular structures of metal-oxide species from their Raman spectra. The state-of-the-art in Raman instrumentation as well as new instrumental developments are discussed in Section 4. Sampling techniques typically employed in Raman spectroscopy experiments, ambient as well as in situ, are reviewed in Section S. The application of Raman spectroscopy to problems in heterogeneous catalysis (bulk mixed-oxide catalysts, supported metal-oxide catalysts, zeolites, and chemisorption studies) is discussed in depth in Section 6 by selecting a few recent examples from the literature. The future potential of Raman spectroscopy in heterogeneous catalysis is discussed in the fmal section. 

To validate the model deduced from the results of these Raman spectroscopy experiments detailed investigations of the Mg/PTCDA system by means of other methods that are highly sensitive with respect to the changes of the chemical environment and charge redistribution such as photoemission spectroscopy were performed [2]. 

Matsoukas and Gulari (17) convincingly showed that the particle mass grows exponentially with the same time constant that describes the first-order hydrolysis of TES. They used the plasma lines in a Raman spectroscopy experiment to observe not only the intensities of the Si-O-Et and Et-OH bands, but at the same time used the light scattering of the particles to follow their growth. The induction period found in the scattering experiments was not found for the hydrolysis reaction. 

To study the structure composite membranes, Raman spectroscopy experiments (a double spectrometer DFS-52, FOMO, Russia) were performed in the quasi-backscattering configuration using the excitation by Ar+ laser (448.8 nm) with the power density of 20 W/cm2. 

In-situ Raman spectroscopy experiments were used to determine effective kinetic propagation constants for a series of unsteady-state divinyl ether polymerisations at different isothermal temperatures and light intensities. A series of Raman experiments were performed on cationic photopolymerisations of a divinyl ether initiated with a diaryliodonium salt of hexafluoroantimonate photosensitised by anthracene. Isothermal Raman experiments were performed for a series of reaction temperatures and were used to determine the overall activation energy of the polymerisation reaction. 20 refs. USA... 

A typical arrangement of a Raman spectroscopy experiment based on the components just outlined is shown in Figure 8.5. As in the case of LIF, the interaction volume can take any form, in principle, like gas cells, low-pressure discharges or flames. Some detection sensitivity problems are encountered if... 

M. Amado, A. M. Amorim da Costa A. M. (2007) Evidence of a local order in concentrated aqueous solutions of salts constituted by ions of different valences X-ray diffraction and Raman spectroscopy experiments. /. Mol. Lujuids 134,1-3,142-150, ISSN 0167-7322... 

Hoskins L C 1984 Resonance Raman-spectroscopy of beta-carotene and lycopene—a physical-chemistry experiment J. Chem. Educ. 61 460-2... 

Nonnal spontaneous Raman scahering suffers from lack of frequency precision and thus good spectral subtractions are not possible. Another limitation to this technique is that high resolution experiments are often difficult to perfomi [39]. These shortcomings have been circumvented by the development of Fourier transfomi (FT) Raman spectroscopy [40]. FT Raman spectroscopy employs a long wavelength laser to achieve viable interferometry. 

Infrared (in) spectrometers are gaining popularity as detectors for gas chromatographic systems, particularly because the Fourier transform iafrared (ftir) spectrometer allows spectra of the eluting stream to be gathered quickly. Gc/k data are valuable alone and as an adjunct to gc/ms experiments. Gc/k is a definitive tool for identification of isomers (see Infrared and raman spectroscopy). 

In the early 1990s Raman spectroscopy was applied to the characterization of TS-1 catalysts [55,56]. In such experiments, beside the 960 cm band, already observed by IR spectroscopy (see Sect. 3.5), a new component at 1125 cm was detected by Scarano et al. [55] (see Fig. 2f). The 1125 cm band was recognized to be a fingerprint of the insertion of Ti atoms in the ze-olitic framework [55]. This band could not be observed in the IR studies as totally overshadowed by an extremely intense band around 1000 cm due to Si02 framework modes (Fig. 2e). 

Time-resolved resonance Raman (TR ) spectroscopy experiments were first reported in 1976 and used a 30 ns pulse radiolytic source to generate the intermediates that were then probed on the microsecond time-scale by a laser source to generate the TR spectrum. TR spectroscopy was then extended to study intermediates... 

Ultrafast time-resolved resonance Raman (TR ) spectroscopy experiments need to consider the relationship of the laser pulse bandwidth to its temporal pulse width since the bandwidth of the laser should not be broader than the bandwidth of the Raman bands of interest. The change in energy versus the change in time Heisenberg uncertainty principle relationship can be applied to ultrafast laser pulses and the relationship between the spectral and temporal widths of ultrafast transform-limited Gaussian laser pulse can be expressed as... 

Hydrogen Abstraction Photoexcited ketone intermolecular hydrogen atom abstraction reactions are an interesting area of research becanse of their importance in organic chemistry and dne to the complex reaction mechanisms that may be possible for these kinds of reactions. Time resolved absorption spectroscopy has typically been nsed to follow the kinetics of these reactions but these experiments do not reveal mnch abont the strnctnre of the reactive intermediates. " Time resolved resonance Raman spectroscopy can be used to examine the structure and properties of the reactive intermediates associated with these reactions. Here, we will briefly describe TR experiments reported by Balakrishnan and Umapathy to study hydrogen atom abstraction reactions in the fluoranil/isopropanol system as an example. 

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