What are the principles of atomic absorption spectroscopy?

Atomic absorption spectroscopy is based on the principles that all free atoms or ions in the ground state can absorb light at specific and unique wavelengths. No other atoms, ions, or elements absorb light at the same wavelength.

Electrons within an atom exist at different energy levels. When an atom is exposed to its specific wavelength of light, it absorbs energy and the electrons move from a ground state to an excited state. 

The amount of radiant energy that an electron absorbs is directly related to the transition that takes place during this process. 

Because every element has a unique electronic structure, it is possible to determine the specific property of each individual element based on the amount of radiation absorbed.