This absorption depends on number of unexcited atoms present and hence, is independent of the flame temperature. It is possible, if the course of radiations is made up of the same element which is going to be analyzed. For e.g. if the sample solution of NaCl is to be analyzed, source of radiations must be Na Vapors.
A brief overview of the process:
1. The solvent is first evaporated leaving fine divided solid particles.
2. This solid particles move towards the flame, where the gaseous atoms and ions are produced.
3. Some of the ions absorb the energy from the flame and excited to high energy levels. Remaining ions will be excited from the external source.
4. So the decrease in intensity of radiation is measured.
5. The decrease in intensity of transmitted light is related to the concentration of the unexcited atoms.
The absorption of radiations follows the Beer-Lamberts Law. As each element absorb the radiations of its own characteristics therefore separate source of radiations is required for each element. $$ \log { \frac { { I }_{ t } }{ { I }_{ 0 } } } =KL{ N }_{ 0 } $$ Where, \({ I }_{ 0 }\) = Intensity of radiations incident.
\({ I }_{ t }\) = Intensity of radiations transmitted.
\(K\) = Characteristics Constant
\(L\) = Path length of flame in cm.
\({ N }_{ 0 }\) = No of atoms in the ground state.
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