Decadic molar absorption coefficient compound

How is the decadic molar extinction coefficient, ,(/l), of a given compound defined What is described by the decadic light absorption or light attenuation coefficient,... 

Electronic Transitions. Since formaldehyde (H2C0) is the simplest carbonyl compound, the CO ir +- n electronic transition of the carbonyl compounds will be briefly described using the formaldehyde transition as the prototype. The lowest singlet state of the CO chromophore of an unconjugated carbonyl can be produced by one-photon absorption of light between 360 and 240 rim (46). This electronic transition is weak, with typical maximum decadic molar extinction coefficient (e) of less than 2 x 10 liters/mol cm. This transition corresponds to the well-known electric-dipole-forbidden vibronically allowed X A ... 

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. 

In Chapter 3 Napierian units were used for absorption coefficients and absorbance. The reason was a simpler handling of the equations. Since instrumentation reads decadic units, they are used in most equations in this chapter. The decadic molar spectral absorption coefficient e of the compounds (i) varies with wavelength A. For this reason Bouguer-Lambert-Beer s law is restricted to monochromatic radiation. This restriction and the interactions between molecules in concentrated solutions cause two problems in applying the law to quantitative evaluation ... 

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