Ultraviolet/visible spectroscopy evaluation

The tautomerism of 4 (Figure 1) was also studied by UV-Vis (ultraviolet-visible) spectroscopy in polar aprotic solvents the effect of added water, darkness, and indirect sunlight were also evaluated. The experimental spectroscopic results are discussed in Section 13.14.3.1.1 (i). Theoretical calculations using ZINDO/S were performed to state the allowed absorption transitions <2005SAA875>. The five tautomeric structures of 4 as well as the calculated energies for each are depicted in Figure 2. 

Low-temperature, photoaggregation techniques employing ultraviolet-visible absorption spectroscopy have also been used to evaluate extinction coefficients relative to silver atoms for diatomic and triatomic silver in Ar and Kr matrices at 10-12 K 149). Such data are of fundamental importance in quantitative studies of the chemistry and photochemistry of metal-atom clusters and in the analysis of metal-atom recombination-kinetics. In essence, simple, mass-balance considerations in a photoaggregation experiment lead to the following expression, which relates the decrease in an atomic absorption to increases in diatomic and triatomic absorptions in terms of the appropriate extinction coefficients. 

Time-resolved spectroscopy (stopped-flow ultraviolet-visible (UV-vis) spectroscopy at -90° C, proprionitrile or acetonitrile, [O2] S> [complex]) has been used to characterize intermediates and evaluate the mechanism of the peroxo complex formation (see Fig. 16) (196). Based on the similarity of the spectral features with known superoxo copper(lI) and peroxo-dicop-per(ll) complexes (262, 268, 281) the mechanism shown in Scheme 17 was proposed, and the spectra of the superoxo copper(II) and peroxo-dicop-per(II) complexes were determined (see Table XI). For steric reasons and in... 

In this regard, various analytical methods have been developed and their potential for the VOO authentication has been evaluated. Thus, spectroscopic tools, such as FT-near-infrared spectroscopy, FT-Raman spectroscopy, fluorescence and ultraviolet-visible detectors, and chromatographic techniques have been widely used in the field of VOO authentication [43-48],... 

The monomers and polymers were characterized by infrared (IR) and ultraviolet-visible (UV-vis) spectroscopy, H and - C nuclear magnetic resonance (NMR), element analyses, differential scanning calorimetry (DSC), and polarizing optical microscopy. The molecular weights of the polymers were evaluated by gel permeation chromatography (GPC) using polystyrene standards, and electrical conductivities upon iodine doping for the cast film of the polymers were measured by the four-probe method. 

The concept of differentiating spectral data was first introduced in the 1950s, but it received little attention primarily because of experimental difficulties in generating derivative spectra with early ultraviolet (UV)/ visible (Vis) spectrophotometers. Use of mathematical or optical methods to generate derivative spectra became feasible with the advent of microprocessors and microcomputers in the late 1970s. Nowadays, most instruments offer at least the first and second numerical derivatives as a standard feature. The combination of derivative spectroscopy and chemometrics for calibration and data evaluation has further increased the popularity of this technique. Derivative techniques are applied especially in UV spectroscopy for pharmaceutical, biomedical, and environmental measurement tasks and in food research. 

Ultraviolet laser ablation Ultraviolet laser desorption/ionisation Ultraviolet photolysis Ultraviolet resonance Raman scattering/spectroscopy Video Image Enhanced Evaluation of Weathering Visible... 

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