Fluorescence lifetime refers to the average time it takes for a fluorophore, a molecule that absorbs light at one wavelength and emits it at another, to return to its ground state after being excited by an external light source.
When a fluorophore is excited by light of a specific wavelength, it temporarily reaches an energetically excited state. It then undergoes relaxation back to its ground state through various processes, one of which is fluorescence emission. The time it takes for the fluorophore to emit a photon and return to its ground state is termed the fluorescence lifetime.
The fluorescence lifetime is influenced by several factors, including the chemical structure of the fluorophore, its local environment, and interactions with nearby molecules. Fluorescence lifetime measurements are valuable in various fields such as biochemistry, biophysics, medical diagnostics, and materials science. They can provide insights into molecular interactions, dynamics, and environmental changes, making fluorescence lifetime a powerful tool for studying biological processes, detecting molecular interactions, and characterizing materials.