Decadic molar absorption species

Decadic molar absorption coefficient of the species X r the warvekngth 5, (liter mol 1 cm 1)... 

Light Absorption by Chemical Species Molar Extinction Coefficients Illustrative Example 15.1 Determining Decadic Molar Extinction Coefficients of Organic Pollutants Chemical Structure and Light Absorption The Fate of Excited Chemical Species Quantum Yields... 

Here /g is the intensity of incident monochromatic radiation, I is the intensity of radiation at a distance I cm, and e is the decadic molar extinction coefficient of an absorbing species (concentration, c mole. 1 ). This law is strictly valid only if molecular interactions are unimportant at all concentrations. Deviations occur for a variety of reasons this means that the validity of the law should be checked under the particular experimental conditions. An initial determination of the absorption spectrum of the compound under investigation is obligatory. This produces immediate qualitative information, particularly about the usefulness of the source of radiation. Banded, diffuse or continuous spectra give direct information about the complexity and variety of primary processes that may occur. Further information will be gained from the effect of radical traps such as Oj or NO, and of various energy transfer agents. 

Point (a) is best optimised by experiment, although several attempts have been made to provide a theoretical basis for determining the optimum concentration of a species of known molar decadic absorption coefficient for resonance Raman studies. The deleterious effects on the signal-noise ratio of the Raman spectram attributable to point (b) can be obviated by spinning the sample at ca. 1600 rev min as a solid, liquid or gas. Several articles contain details of many of these devices, the common object of which is to ensure relative motion between the sample and the focused laser beam (64). Surface scanning devices are also in use, and these enable the laser beam, while remaining focused on the surface of the sample, to scan over its surface in either a circular or linear fashion to achieve the same object. Such a procedure is particularly effective when the sample is held at liquid nitrogen temperatures. A device which allows this mode of operation is shown in Fig. 10 in this case the laser beam... 

Here, i]ppp indicates the luminescence efficiency of the donor, n is the refractive index, Aem, > is the normalized emission spectrum of the donor in the absence of acceptor species, A hs.D corresponds to the absorption spectrum of the acceptor (more precisely, the molar decadic extinction coefficient of the acceptor), v is the frequency wavenumber and k is a factor related to the orientation of the donor and the acceptor dipole moments, k is of the order of unity, and an average value of k = 2/3 is used most of the time, corresponding to dipole moments that are randomly distributed over all orientations. While... 

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