Fluorescence is emitted at wavelengths longer than the exciting radiation. Both the absorbed and emitted wavelengths are characteristic of a given molecule. Because the emitted wavelength is different than the exciting wavelength, fluorescence detection is very sensitive relative to absorption measurements. In some cases LIF sensitivities approach the detection of a single atom or molecule. In the biological arena, LIF is used for early cancer detection, to study atherogenesis, and to track gene expression.
Scientists are able to access very exciting information through fluorescence microscopy imaging.
That is, they can monitor processes happening in a living cell. Much will be learned about the connection of genetic defects and hereditary diseases and proteomics or the actions of proteins in a cell. Physical chemists employ LIF in studies of the electronic structure of molecules. LIF based handheld instruments screen for surface uranium contamination. LIF is used for airborne hyperspectral imaging to monitor vegetation status and water pollutants.