UV-vis spectral range

Such enantiomerically pure chiral compounds, which are optically inactive in the generally investigated UV/Vis spectral range from 200 to 800 nm, can be designated as cryptochiraF according to Mislow et al., since the chiral information is hidden in the molecule (i.e. present in cryptic form) [12a, 20]. Cryptochirality of the dendrimer is explained on the one hand by the pronounced conformational mobility of the dendrimer branches and on the other by the slight electronic difference between the dendritic substituents. 

In solutions, the energy of the 4f—> 5d transitions is lowered by about 15000 cm-1 as compared to gaseous ions and the corresponding parity allowed and relatively intense bands are observed in the ultraviolet region in Ce3+, Pr3+ and Tb3+ ions. As shown in Fig. 8.14, the electronic absorption spectra of the majority of the trivalent lanthanides in the UV-vis spectral range involves only f-f transitions. 

Rella et al. used spin-coated films of three zinc phthalocyanines as optochemi-cally interactive materials for the detection of amines in the UV-vis spectral range... 

Rigorously, the above Floquet representation is valid only when the field is periodic. Imagine now that the field amplitude Eo in Eq. (12) carries a time dependence that denotes a slow modulation of the cosine field which oscillates with a frequency in the UV-Vis spectral range. Without the amplitude modulation, the dynamics under the UV-Vis field is well captured by the Floquet representation. If the amplitude modulation is slow. 

ECD, VCD, Raman optical activity (ROA), and ORD are at disposal in a spectral range between the IR and the vacuum UV. ACD and AORD, the CD and ORD of chiral anisotropic phases are only available in the UV/vis spectral range. The specific rotation, as a standard, is measmed with the sodium D-line. For special applications other lines, e.g., mercury lines, have been taken. Indirect methods for chiroptical analyses are the nuclear magnetic resonance (NMR) spectroscopy of diastereomeric compounds and the chiral induction of cholesteric phases (helical twisting power (HTP)) combined with ACD/ CD and the corresponding selective reflection. 

One remarkable property of G is transparency to the light in almost the whole UV-vis spectral range. Single layer G supported on a transparent substrate should absorb a minute amount of light and the transmittance... 

When fluorescence spectra having different shapes and X. distributions are to be compared quantitatively it is necessary to correct for the wavelength-dependent sensitivity of the EmW MT combination. If the spectra of a solute under different sample conditions have identical shape and only vary in intensity, then no instrumental correction is necessary. PMTs do not have constant photon sensitivity across the useful UV-VIS spectral range. A typical photon sensitivity curve is shown in Figure 10 for a Hamamatsu R955 PMT, a PMT that is used in many instruments. It would be desirable is to have a flat wavelength response. 

The UV region spectrally ranges from about 180 to 400 nm, the VIS spectrum from 380 to 780 nm, and the IR from 780 nm to 1mm. The actual point of separation between the (UV)-A and VIS region frequently overlaps. 

Fig. 19 UV-VIS spectral change of PPE-SOj as a function of SPG concentration (concentration range of s-SPG 0-6.7 x 10 M). The concentration of PPE-SOj was kept at 1.5 X 10 M. H2O/DMSO = 95/5 (v/v), 1.0 cm cell length, room temperature. Reprinted with permission from [114]...

Q, Qy low-energy absorption bands of tetrapyrroles in the Vis/NIR spectral region RC reaction center (Type I and Type II relate to the homologies with PSI and PSII, respectively) UV ultraviolet spectral range (200 to 400 nm)... 

One of the earliest applications of the Kalman filter in analytical chemistry was multicomponent analysis by UV-Vis spectrometry of time and wavelength independent concentrations, which was discussed by several authors [7-10]. Initially, the spectral range was scanned in the upward and downward mode, but later on... 

Addition of H202 or t-BuOOH to aqueous solutions of iron(III)-TAML complexes 1 produces brownish-green colors. The spectral changes can be measured by UV/Vis spectroscopy (Fig. 10). Less than a stoichiometric amount of peroxide causes a major increase in the absorbance in the range 350-550 nm. It requires several minutes to obtain invariable spectra at pH below 8.5, but the reaction becomes much faster at pH >9. Two isosbestic points... 

There are numerous excitation sources available for LIF instruments. A xenon arc lamp is the most common light source within commercial LIF analyzers. While they offer uniform broad spectral coverage across the UV-vis range and sufficient uniform power output, they are low precision sources and do not offer sufficient real-time or dynamic optical power control. The white output also necessitates an excitation... 

The application of standardized UV (or UV-Vis) spectroscopy has for years been used in analyses of flavonoids. These polyphenolic compounds reveal two characteristic UV absorption bands with maxima in the 240 to 285 and 300 to 550 nm range. The various flavonoid classes can be recognized by their UV spectra, and UV-spectral characteristics of individual flavonoids including the effects of the number of aglycone hydroxyl groups, glycosidic substitution pattern, and nature of aromatic acyl groups have been reviewed in several excellent books. ... 

Absorption spectra have also been used in the reexamination of pH-dependent color and structural transformations in aqueous solutions of some nonacylated anthocyanins and synthetic flavylium salts." ° In a recent study, the UV-Vis spectra of flower extracts of Hibiscus rosasinensis have been measured between 240 and 748 nm at pH values ranging from 1.1 to 13.0." Deconvolution of these spectra using the parallel factor analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species (Figure 2.21). The model allowed identification of seven anthocyanin equilibrium forms, namely the flavylium cation, carbinol, quinoidal base, and E- and Z-chalcone and their ionized forms, as well as their relative concentrations as a function of pH. The spectral profiles recovered were in agreement with previous models of equilibrium forms reported in literature, based on studies of pure pigments. 

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