Wavelength of absorption

Calculation can also explain why in some thiazole dyes vinyiene shift of the first two homologs is larger than the shift between higher members of the series, and also why wavelengths of absorption of nonsymmetrical dyes as calculated by the mean value rule differ from experimental data (6671. This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. 

TABLE 7.2 Wavelengths of Absorption Edges in Angstroms (Continued)... 

Phenylation of tfie piimaiy amino groups also produces an increased bathochromic shift in the wavelength of absorption with increasing degree of phenylation. Only monophenylation of each amino group is possible, eg, as in (6) and (7). 

SAMSA-fluorescein is an orange solid compound. Dissolved in buffer at pH 9.0, its maximal wavelength of absorption or excitation is at 495 nm, while its emission wavelength maximum is 520 nm. The reagent and all solutions and derivatives made from it are light sensitive and should be stored in the dark. SAMSA-fluorescein is soluble in aqueous solutions above pH 6.0, but it can be dissolved in DMF to prepare a concentrated stock solution prior to adding a small amount to a buffered reaction mixture. 

Ultraviolet spectra. The absorption in compounds containing conjugation is due to n-n transition and the longer the conjugation the longer is the wavelength of absorption. 

Is the wavelength of fluorescence longer or shorter than the wavelength of absorption Explain your answer with the help of an energy level diagram. 

One is needed to select the wavelength of absorption and one to select the wavelength of fluorescence. 

Fig. 2 Chemical structures of fluorescent ligands (anion coordination sites are indicated in blue) and tentative reaction schemes on interaction of 6 with chloride and fluoride in dichloromethane according to the color patterns observed in [41]. The wavelengths of absorption given in brackets have been calculated for the geometry optimized species 6, 6-C1 and 6 in the gas phase by semiempirical AMI calculations (Ampac V6.55, Semichem)...

More explicitly, the absorption by atom is independent of both the wavelength of absorption and the temperature of the atoms. And these two specific characteristic features give AAS a clear distinct and positive edge over FES. 

Peak wavelengths of absorption and emission for different fiuoro-conjugated antibodies... 

Several other laser lines have already been used in a similar way 2-90) to measure absorption coefficients and absolute wavelengths of absorption lines, as well as the line profiles and possible fine structures of many polyatomic molecules. By substituting different isotopes, the isotopic shift of absorption lines has been studied Table 2 shows some of the molecules investigated by the laser line absorption technique, together with the exciting laser wavelengths and some remarks about the kind of measurements performed. 

A dye appears coloured because one or more components of the light falling upon it are absorbed so that the reflected light is deficient in certain colours. The wavelength of absorption is dependent upon the degree of conjugation i.e. the number of alternate single and double bonds within the molecule). 

In recent years metliines, hemicyanines and cyanines have been the subject of much research as they couple high molar absorption and emission coefficients with a relative ease of molecular manipulation to change the wavelength of absorption, making them an obvious target for chemical designers. 

Wide variation of the donor gronps on the squarylium dyes of structure type (4.6) only gave a maximnm wavelength of absorption of 708 mn, and it was necessary to nse the strongly electron-donating dihydroperimidine ring system to achieve absorption fully into the near-IR, as exemplified by (4.8), 800-810 nm, 150 000. °... 

In electronic spectroscopy, one wants to know not only the energy difference between distinct electronic states but also the probability that a transition between them will take place under appropriate circumstances. Thus, in the recording of a classic UV/Vis spectrum for a molecule, the wavelengths of absorptions indicate the energetics of the transition, while the intensities of the absorptions indicate their aliowedness , or probability. 

The chromophore is not only extended by conjugation the presence of an electron-donating substituent on an aromatic ring also has the effect of increasing the wavelength of absorption, as we can see for the examples in Box 2.1. 

A good absolute theoretical comparison of strength is represented by the area under the absorption bands in the visible spectrum, or less accurately by the molecular extinction coefficients at the maximum wavelength of absorption. 

In addition to the aromatic amino acids, several others have absorption maxima in the UV range. Table B1.3.1 shows the wavelengths of absorption maxima and corresponding molar absorptivity (e) for the amino acids with appreciable absorbance in the UV range. Only tryptophan has an absorption maximum at 280 nm. 

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