Coefficients of extinction

The ultra-violet absoiption spectra of nearly 60 nitramines were examined by R. N. Jones and Thom, who drew up an interesting rule about the coefficient of extinction for nitramines. 

More than 30 years ago, Scott, Obenhaus, and Wilson (135) suggested that for lithium chloride, a solute to solvent ratio of 1 10 corresponded to a definite composition, and they quoted earlier measurements (134) as indicating two distinct, definite values for the magnetic susceptibility of lithium chloride above and below the concentration, corresponding to a decahydrate in solution. Likewise, anomalies were also found in the density of such solutions. Scott, Obenhaus, and Wilson also quoted Hiittig and Keller (83) who found that the densities, refractive indices, and coefficient of extinction of lithium halide solutions showed discontinuous changes with concentration for molar ratios of water to solute of 6, 30, and 75. 

Accomplishment of the complex observational experiment LACE-98 made it possible to obtain extensive information about atmospheric aerosol (aircraft measurements of the size distribution and number density of fine aerosols, coefficients of aerosol absorption, backscattering and depolarization, chemical composition of aerosol, as well as surface observations of the spectral optical thickness of the atmosphere, coefficients of extinction and backscattering). Fiebig et al. (2002) compared the observational data on optical parameters obtained from the results of numerical modeling for total H2S04 aerosol near the tropopause as well as for the ammonium sulfate/soot mixture in the remainder of the air column (Osborne et al., 2004). 

This expression is comparable with Beer-Lambert s law for the absorption of non-scattering samples. Both in the theory of Kubelka and Munk and in Beer-Lambert s law the relationship derived from the measurement value is proportional to the coefficient of absorption and hence proportional to the concentration (c) and coefficient of extinction Sn of the absorbing material ... 

The coefficient of extinction r mentioned here is approximately comparable but not identical with the coefficient of extinction in Beer-Lambert s law. r is dependent on an interaction between the absorbing molecules and the reagent carrier matrix. 

The values we found for the molar coefficient of extinction were nearly 14-times higher than the value determined from the UV-spectrum at wavelength s 340 nm, corresponding to the maximum of the adsorption band for 2,2-diizopropyloxyacetophenone (DiPAPh). 

The sharp bands of low intensity are characteristic for such ions (the molar coefficients of extinction, e = 1-10) in this range. The molar coefficients of extinction for CgHg -complexes are 10-1(X) times larger than those for the f-f-transitions of aqua-ions, and the absorption bands for them are essentially broader. This difference suggests that the visible spectra of CgHg lanthanoid complexes are determined in the whole not by the f-f transitions but due to a charge transfer from the ligand to the metal [30, 31, 34, 37]. 

The electron absorption spectrum of the chlorophylls and their derivatives is very characteristic and is attributed to the system of conjugated double bonds making up the basic porphyrin structure. Electron transitions in the chlorophyll molecules, detected by photosensitive optical equipment, produce absorption bands [8,64,65], The intensity of a particular absorption band is normally expressed by its molar specific coefficient of extinction s), which, according to the Beer-Lambert law, depends on the optic density (A), the molar concentration (C), and the optical pathway of the light beam through the solution, expressed in centimeters (L). 

Detection is normally by absorption or fluorescence spectrophotometry. The high coefficients of extinction of the chlorophyll Soret band enable sensitive detection between 380 and 445 nm. This region of the spectmm also includes the carotenoids, which accompany the chlorophylls in plant pigment extracts and whose analysis and quantification are also usually of interest (see Chapter 6). When these compounds are not of interest, and their possible interference must be excluded, a selective detection of chlorophylls and derivatives can be carried out at 654 [136] or 667 nm [230], where there is no absorption of these pigments. Detection... 

L is the optic pathway through the solution, expressed in centimeter e is the molar coefficient of extinction... 

The coefficients of extinction in acetone for each pigment are calculated from those given in the bibliography for chlorophylls and pheophytins in ethyl ether [194] by using a pigment solution of known concentration. It is assumed that the coefficients of extinction of compounds with different chemical structure but identical electron absorption spectrum (e.g., chlorophyll/chlorophyllide) do not differ significantly [251]. Thus, the specific coefficient of extinction (e ) can be calculated from a known molar coefficient (st) of another compound (i) with an identical spectrum ... 

Here, I is the length of the path, c is the concentration of the absorbing species, and e is the coefficient of extinction with respect to the particular absorbing species. 

Determination of film Thickness. The thickness of the dry films was calculated from the measured absorbance of the dye in the glass, the coefficient of extinction, the dye concentration and the density of the glass film (measured to be ca. 1.3 g/cm ). Direct measurements were carried out with an Inverted-Stage Epifluorescent Video Microscope (Leitz Fluovert Rockleigh, NJ). 

Absorptivity (optics) The absorption of radiation as it passes through a material. See also Coefficient of extinction. 

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