ABSTRACT
Fluorescence is the property of some atoms and molecules to absorb light of a particular wavelength and after a brief interval, termed the fluorescence lifetime, to re-emit light at longer wavelengths. Fluorescence requires an outside source of energy, is the result of the absorption of light, and involves the emission of electromagnetic radiation. This process is different from chemiluminescence, where the excited state is created via a chemical reaction. The absorption of a photon of energy by a fluorescent molecule is an all or none phenomenon and each fluorescent molecule can only absorb incident light of certain specific wavelengths known as absorption bands. Since the amount of fluorescence is proportional to the excited state population of singlets, to measure the fluorescent lifetime, we can interrogate the population by asking how fast fluorescence decays after a pulse of excitation.
