Maxima of absorption

In practice, the wavenumbers vAh and vA- corresponding to the 0-0 transitions of AH and A are often difficult to determine accurately. They are usually estimated by means of the average between the wavenumbers corresponding to the maxima of absorption and emission ... 

Table 6 Maxima of absorption and extinction coefficients of model and growing carbenium ions...

Slow neutrons (neutrons with energies of the order of 1 eV to 1 keV are also called resonance neutrons, because maxima of absorption are observed in this energy range)... 

The spectral positions of the 0 O bands of absorption and fluorescence usually do not coincide exactly. The difference is called the Stokes shift. The excited state is generally more polarizable and often more polar than the ground state. Solvent relaxation then stabilizes the excited state following Franck Condon excitation, so that the 0 0 band of absorption is usually at higher frequency than that of emission. When the excited state is much less polar than the ground state, the 0 0 band of fluorescence may appear at higher frequency than that of absorption anti-Stokes shift). Unfortunately, the term Stokes shift is also used to refer to the gap between the band maxima of absorption and emission (see the footnote to fluorescence in Section 2.1.1), which may be much larger than the shift between the 0 0 bands. 

The position of the absorption band is shifted slightly to the red with an increasing number of alkyl substituents. The maxima at 174-184.5 nm found for Z-l,2-disubstituted olefins are shifted to the red in E-isomers by 3-4nm and reach 186-189nm in 1,1-disubstituted olefins. Maxima of absorption bands are observed at 177-191 nm for trisubstituted and at 187-191 nm for tetrasubstituted olefins. The position of the maximum of the V - N band is further shifted to the red by a few nanometers in olefins with sterically demanding substituents like 66, 255b, and 263b. 

TABLE 4 Maxima of Absorption Spectra of tram and cis Isomers"... 

Table 17 Maxima of absorption spectra in the visible (and corresponding molar absorptivities ), fluorescence, and phosphorescence spectra, lifetimes of S 2 SoandS - Sq fluorescence and T2 Sq phosphorescence, and S 2 energy gaps estimated from...

The structure of synthesized polyetherimides has been confirmed with the data of the IR-spectral analysis. Particularly, IR-spectra of polyetherimides based on l,l-dichlor-2,2-di(p-oxiphenyl)ethylene contain maxima of absorption in the range from 840 up to 980 sm attributed to 1,1-dichlorethylene groupings [10], All spectra of polyethemaphtalimides contain doublets at 1738-1745 and 1780-1785 sm , characteristic for carbonyl groups of six-member anhydride cycle Besides the strips of absorption caused by presence of bridge groupings occur in IR-spectra 1260 sm (-0-) and 1645-1680 sm (-CO-). 

In water-in-[Bmim][PFg] microanulsions at Wq = 2, C-153 shows absorption peak at 426 nm. With an increase in Wq value the peak maxima of absorption gradually increase. Whereas, C-151 in water shows absorption peak at 364nm. In microemnlsions the absorption peak of C-151 appeared at 370nm. With an increase in Wq the absorption peak of C-151 remains unchanged. The representative absorption maxima of C-153 and C-151 in microemulsions are tabulated in Table 8.6. 

Not only the stationary band maxima of absorption and fluorescence match this formula but also the radical absorption and even the triplet and singlet excited state absorption. Thereby the fitting parameters have been altered. 

Fig. 331. Maxima of absorption spectra of polyenes as a function of the number of conjugated double bonds [1634],...

In the diatoms, the relative percentages of chlorophylls a and C1/C2 are close to 50/50. The wavelengths of the maxima of absorption in acetone are respectively 666, 647, 392, and 372 nm for chlorophylls a, b, Ci, and C2. This allows a simultaneous measurement of the different chlorophylls in the same extract (Meeks, 1974 Jensen, 1978 Sterman, 1988). At least for the species Chaetoseros calcitrans, the acrylate group at the 17-position enhances the absorption region of chlorophylls ci and C2 (Mizoguchi et al, 2009). 

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