Intensity extinction coefficient

Chemosensor A molecular or supramolecular entity responding to analytes, usually following a molecular recognition event, by changes in photophysical parameters (absorbance/emission wavelength/intensity, extinction coefficient, emission lifetime, quantum yield). 

The intensity of a spectral absorption band at a given wave length is expressed in terms of absorption or extinction coefficients, dehned on the basis of the Beer-Lambert law. The latter states that the fraction of incident light absorbed is proportional to the number of molecules in the light path, i.e., to the concentration (c) and the path length (1). The law may be expressed mathematically as ... 

The absolute intensity of an absorption band may be expressed by giving the value of em x., the molecular extinction coefficient at the wave... 

The electronic transitions which produce spectra in the visible and ultraviolet are accompanied by vibrational and rotational transitions. In the condensed state, however, rotation is hindered by solvent molecules, and stray electrical fields affect the vibrational frequencies. For these reasons, electronic bands are very broad. An electronic band is characterised by the wave length and moleculai extinction coefficient at the position of maximum intensity (Xma,. and emai.). 

The vibration frequencies of C-H bond are noticeably higher for gaseous thiazole than for its dilute solutions in carbon tetrachloride or tor liquid samples (Table 1-27). The molar extinction coefficient and especially the integrated intensity of the same peaks decrease dramatically with dilution (203). Inversely, the y(C(2jH) and y(C(5(H) frequencies are lower for gaseous thiazole than for its solutions, and still lower than for liquid samples (cf. Table 1-27). 

K Fe(CN)6 oxidation Compound F is stoichiometrically inactivated by oxidation with K.3Fe(CN)6 (Shimomura and Johnson, 1967) thus, it is possible to estimate the molecular extinction coefficient (e) of the 388-390 nm absorption peak by titrating F with K.3Fe(CN)6- The e value obtained by the titration in 50% ethanol was 15,400 (assuming the reaction to be one-electron oxidation) or 30,800 (assuming two-electron oxidation). Two other methods of lesser precision were used to determine the true s value 1) the dry weight of the ethyl acetate extract of an acidified solution of F gave an e value of 14,100 2) the comparison of NMR signal intensities gave a value of 11,400 2,000 in water (H. Nakamura, Y. Oba, and A. Murai, 1995, personal... 

Billmers and Smith recorded the UV-Vis absorption spectra of sulfur vapor at various pressures (9-320 Torr or 1.2-42.7 kPa) and temperatures (670-900 K) but failed in obtaining the correct reaction enthalpy for the interconversion of S3 and S4 from the absorption intensities [19]. The molar extinction coefficient of S3 at 400 nm exceeds that of S4 at 520 nm by more than one order of magnitude. While the S3 absorption band at 360-440 nm exhibits a vibrational fine structme, the two broad S4 absorption bands at... 

Chemical methods for structure determination in diene pol3 mers have in large measure been superseded by infrared absorption techniques. By comparing the infrared absorption spectra of polybutadiene and of the olefins chosen as models whose ethylenic structures correspond to the respective structural units, it has been possible to show that the bands occurring at 910.5, 966.5, and 724 cm. are characteristic of the 1,2, the mns-1,4, and the m-1,4 units, respectively. Moreover, the proportion of each unit may be determined within 1 or 2 percent from measurements of the absorption intensity in each band. The extinction coefficients characteristic of each structure must, of course, be known these may be assigned from intensity measurements on model compounds. Since the proportions of the various units depend on the rates of competitive reactions, their percentages may be expected to vary with the polymerization temperature. The 1,2 unit occurs to the extent of 18 to 22 percent of the total, almost independent of the temperature, in free-radical-polymerized (emulsion or mass) poly butadiene. The ratio of trans-1,4 to cfs-1,4, however,... 

Quantitative analysis of the absorption intensity affords values of the formation constants (Kda) and extinction coefficients (act) listed in Table 1 for comparison with the corresponding characteristics of the bromide complexes with tetrabromomethane. 

A useful measure of the strength or intensity of the colour of a dye is given by the molar extinction coefficient (e) at its 2max value. This quantity may be obtained from the UV/visible absorption spectrum of the dye by using the Beer-Lambert law, i.e. 

The experimental findings of the optical density in the absorption region of the C=0 group (1770 cm-1 at a layer thickness of h = 0.87 x 10 4 cm), of the molar extinction coefficients of irradiated and non-irradiated copolymer films, and of the intensities of absorbed light (= 405 nm) made it possible to determine the quantum efficiency of C=0 group consumption using the known equation... 

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