Atomic Spectroscopy: Absorption, Emission, and Fluorescence

Atomic spectroscopy is an analytical tool for qualitative and quantitative elemental analysis.

The main types include atomic absorption spectroscopy, or AAS; atomic emission spectroscopy, or AES; and atomic fluorescence spectroscopy, or AFS.

All three methods begin with atomization, which is the critical step of breaking down liquid samples into gas-phase atoms.

In AAS, hot gaseous samples irradiated with a range of electromagnetic radiation absorb light of the specific wavelengths that cause electronic transitions in the atoms to higher-energy orbitals.

The amount of light transmitted at each wavelength is measured by the detector. 

In AES, the input of heat or electrical discharge on the ground-state gaseous atoms causes electronic excitation.

These high-energy atoms quickly return to the ground state, emitting photons that match the energy differences.

In AFS, the ground-state gaseous atoms are irradiated at a characteristic wavelength for promotion of a specific atom to the excited state.

If the atom is present, it fluoresces, which is measured by a detector placed at a right angle to the laser beam.