Fluorescence

Patent Pending Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It also occurs when molecules are excited to higher electronic states by energetic electron bombardment, such as occurs, for example, in the natural aurora[clarification needed], high-altitude nuclear explosions, and rocket-borne electron gun experiments.[1] It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons; this two-photon absorption can lead to emission of radiation having a shorter wavelength than the absorbed radiation. The emitted radiation may also be of the same wavelength as the absorbed radiation, termed "resonance fluorescence".[2]