Raman Extracting

Diamond is crystallized in cubic form (O ) with tetrahedral coordination of C-C bonds around each carbon atom. The mononuclear nature of the diamond crystal lattice combined with its high symmetry determines the simplicity of the vibrational spectrum. Diamond does not have IR active vibrations, while its Raman spectrum is characterized by one fundamental vibration at 1,332 cm . It was found that in kimberlite diamonds of gem quality this Raman band is very strong and narrow, hi defect varieties the spectral position does not change, but the band is slightly broader (Reshetnyak and Ezerskii 1990). 

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I CRS interferogram with a frequency of A = coj + 2c0j - cOq, where cOp is the detected frequency, coj is the narrowband frequency and coj the Raman (vibrational) frequency. Since cOq and coj are known, Wj may be extracted from the experimentally measured RDOs. Furthemiore, the dephasing rate constant, yj, is detemiined from the observed decay rate constant, y, of the I CRS interferogram. Typically for the I CRS signal coq A 0. That is, the RDOs represent strongly down-converted (even to zero... 

The key for optimally extracting infonnation from these higher order Raman experiments is to use two time dimensions. This is completely analogous to standard two-dimensional NMR [136] or two-dimensional 4WM echoes. As in NMR, tire extra dimension gives infonnation on coherence transfer and the coupling between Raman modes (as opposed to spins in NMR). 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

Because Raman spectroscopy requires one only to guide a laser beam to the sample and extract a scattered beam, the technique is easily adaptable to measurements as a function of temperature and pressure. High temperatures can be achieved by using a small furnace built into the sample compartment. Low temperatures, easily to 78 K (liquid nitrogen) and with some diflSculty to 4.2 K (liquid helium), can be achieved with various commercially available cryostats. Chambers suitable for Raman spectroscopy to pressures of a few hundred MPa can be constructed using sapphire windows for the laser and scattered beams. However, Raman spectroscopy is the characterizadon tool of choice in diamond-anvil high-pressure cells, which produce pressures well in excess of 100 GPa. ... 

NMR, Raman and IR spectroscopy are most frequently used to investigate the complex structures of fluoride solutions containing tantalum and niobium. Most investigations of such solutions were performed on the liquid-liquid extraction of tantalum and niobium, with the objective of describing the mechanism of the process. These publications will be discussed separately. 

In the conclusion of the present chapter we show how comparison of NMR and Raman scattering data allows one to test formulae (3.23) and (3.24) and extract information about the relative effectiveness of dephasing and rotational relaxation. In particular, spectral broadening in nitrogen caused by dephasing is so small that it may be ignored in a relatively rarefied gas when spectrum collapse proceeds. This is just what we are going to do in the next sections devoted to the impact theory of the isotropic Raman spectrum transformation. 

In the pioneering work the same information was extracted from the extremum position assuming it is independent of y [143]. This is actually the case when isotropic scattering is studied by the CARS spectroscopy method [134]. The characteristic feature of the method is that it measures o(ico) 2 not the real part of Ko(icu), as conventional Raman scattering does. This is insignificant for symmetric Lorentzian contours, but not for the asymmetric spectra observed in rarefied gas. These CARS spectra are different from Raman ones both in shape and width until the spectrum collapses and its asymmetry disappears. In particular, it turns out that... 

Insoluble sulfur obtained by CS2 extraction of commercial Crystex N data taken from conventional Raman studies using an Ar laser [177]... 

VEDAVANAM K, SRIJAYANTA s, o reilly j, RAMAN A, WISEMAN H. (1999) Antioxidant action and potential antidiabetic properties of an isoflavonoid-containing soyabean phytochemical extract (SPE). Phytother Res. 13 601-8. 

High performance spectroscopic methods, like FT-IR and NIR spectrometry and Raman spectroscopy are widely applied to identify non-destructively the specific fingerprint of an extract or check the stability of pure molecules or mixtures by the recognition of different functional groups. Generally, the infrared techniques are more frequently applied in food colorant analysis, as recently reviewed. Mass spectrometry is used as well, either coupled to HPLC for the detection of separated molecules or for the identification of a fingerprint based on fragmentation patterns. ... 

In order to extract the contributions and dynamics of the ketyl radical and fluoranil anion from the TR spectra obtained with the 416 nm probe wavelength, a deconvolution of the Raman bands were done using a fitting procedure employing a Lorentzian lineshape for the Raman bands of the two intermediates. Figure 3.20 shows a comparison of the best-fit (lines) to the experimental TR spectra (dots) in the left-side spectra and the deconvolution extracted from this best fit for the ketyl radical spectra... 

Kazarian et al. [281-283] have used various spectroscopic techniques (including FUR, time-resolved ATR-FHR, Raman, UV/VIS and fluorescence spectroscopy) to characterise polymers processed with scC02. FTIR and ATR-FTIR spectroscopy have played an important role in developing the understanding and in situ monitoring of many SCF processes, such as drying, extraction and impregnation of polymeric materials. 

Principles and Characteristics Vibrational spectroscopic techniques such as IR and Raman are exquisitely sensitive to molecular structure. These techniques yield incisive results in studies of pure compounds or for rather simple mixtures but are less powerful in the analysis of complex systems. The IR spectrum of a material can be different depending on the state of the molecule (i.e. solid, liquid or gas). In relation to polymer/additive analysis it is convenient to separate discussions on the utility of FUR for indirect analysis of extracts from direct in situ analysis. 

In polymer/additive deformulation (of extracts, solutions and in-polymer), spectroscopic methods (nowadays mainly UV, IR and to a lesser extent NMR followed at a large distance by Raman) play an important role, and even more so in process analysis, where the time-consuming chromatographic techniques are less favoured. Some methods, as NMR and Raman spectrometry, were once relatively insensitive, but seem poised to become better performing. Quantitative polymer/additive analysis may benefit from more extensive use of 600-800 MHz 1-NMR equipped with a high-temperature accessory (soluble additives only). 

In addition to quantitative crystallinity data, IR and Raman have been proven valuable tools to extract information on chain conformation in the three major phases [112-114], local order in amorphous polymers [115,116] high throughput characterization [117] and structural and polymorphic changes on heating and cooling semi-crystalline polymers [118-120]. 

For oriented systems, the determination of molecular conformation is a complex problem because Raman spectra contain signals inherently due to both molecular conformation and orientation. To extract only the information relative to the conformation, one has to calculate a spectrum that is independent of orientation, in a similar way to the A0 structural absorbance of IR spectroscopy (Section 4). Frisk et al. [57] have shown that for a uniaxial sample aligned along the Z-axis, a spectrum independent of orientation (so-called isotropic spectrum), fso, can be calculated from the following linear combination of four polarized spectra [57]... 

The vibrational frequency of the special pair P and the bacteriochlorophyll monomer B have also been extracted from the analysis of the Raman profiles [39,40,42,44,51]. Small s group has extensively performed hole-burning (HB) measurements on mutant and chemically altered RCs of Rb. Sphaeroides [44,45,48-50]. Their results have revealed low-frequency modes that make important contribution to optical features such as the bandwidth of absorption line-shape, as well as to the rate constant of the ET of the RCs. 

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