Luminescence - Fluorescence And Phosphorescence, Processes That Create Luminescence, Thermoluminescence, Porous Silicon
light luminescent energy fluorescent
Light generation by a process other than by heating is luminescence. For example, an incandescent light bulb, in which the filament is heated until it is literally white-hot, is not luminescent; a fluorescent light tube (which is cool to the touch) is luminescent. Luminescence is generated as part of a process in which atoms or molecules with electrons excited into higher energy states shed energy by emitting visible light.
People have observed luminescence in nature for centuries. In the early twentieth century, Marie Curie, in her doctoral thesis, mentioned that calcium fluoride glows when exposed to the radioactive material, radium. In the past 50 years, the use of luminescent devices, such as fluorescent lights and television screens, has become widespread.
Additional Topics
Luminescence can be divided into categories by duration (fluorescence or phosphorescence) or by the mechanism that creates the light. By definition, fluorescent things stop emitting light very soon (about 10 ns) after the exciting energy is cut off. Phosphorescence continues for longer than fluorescence. Glow-in-the-dark stickers and watch hands that glow are examples of phosphorescence. A less ob…
Other types of luminescence are defined by the source of the energy that causes the light emission. These include chemiluminescence, bioluminescence, electroluminescence, sonoluminescence, triboluminescence, and thermoluminescence. Chemical reactions provide the energy to generate photons in chemiluminescence. These chemical reactions often involve oxygen. Cyalume sticks are chemiluminescent: when…
In the early 1990s, L. T. Canham at the Royal Signal and Radar Establishment in England reported luminescence from porous silicon. This generated great interest, because if the luminescence could be controlled, then light-emitting devices could be integrated with silicon microelectronics. Although silicon photodetectors had been made, the material had not been known to emit light before. This coul…
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