General Principle of Absorption

The basic description of the attenuation of radiation by passing an absorbing volume is given by Beer s law  

The spectrum of the transmitted radiant power shows the absorption line of the gaseous atoms centered at wavelength Ao, and the absorption coefficient in Beer s law becomes dependent on the wavelength  

The shape of k X) is determined by the effects of Doppler and collisional broadening (refer to Section 2.1). For the quantity one can use the results of the classical radiation theory [105], which provides the correlation between fc(A) and N, where N denotes the volume concentration of absorbing atoms in the ground state  

The factor / represents the so-called oscillator strength given by quantum mechanical relationships the symbols e and m denote the electron charge and the electron mass, respectively. In order to obtain a result directly proportional to the number of atoms, the radiant power absorbed at the absorption line has to be measured in AAS, i.e. the incident 4 o) as well as the transmitted 4 x) radiant power have to be ascertained. Equation 2.18 can be modified as follows  

The dimensionless number for absorbance A is also called optical density. Standardized line profiles may be used as function k. The absorbance A is proportional to the number of atoms in a volume with concentration of absorbing atoms N, and length /. 

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