In atomic fluorescence spectroscopy, or AFS, atomized samples are irradiated by electromagnetic radiation to cause electronic transitions, and the emitted fluorescence radiation is measured.

The AFS instrument has a high-intensity light source, an atomizer, a wavelength selector, and a detector. Potential excitation sources include pulsed hollow-cathode lamps, electrodeless-discharge lamps, xenon or mercury arc lamps, and lasers.

Like in AAS, the analyte is atomized and then excited by the light source. The excited atoms release energy by fluorescence at wavelengths representing specific atomic species to return to their lower energy states.

Because atoms fluoresce at their optimal absorption wavelength, the source beam is at a right angle to the detector—usually a photomultiplier tube.

The fluorescence intensity is proportional to the target element's concentration. It is also proportional to irradiation intensity, making high-intensity sources and minimal interfering radiation essential.

Still, AFS is particularly effective for identifying volatile-hydride-forming elements and mercury.

Further, chemical and spectral interferences from atomization can be avoided by adding releasing or protective agents to the matrix.