Photoluminescence

Photoluminescence is light emission from matter after absorbing photons. It is a form of luminescence initiated by , where photons excite electrons to a higher energy level in an atom. After excitation, various mechanisms release the absorbed energy as new photons. Time between absorption and emission varies, ranging from femtoseconds for free-carrier plasma in inorganic semiconductors or metals to milliseconds for phosphorescence. Under special circumstances the emission delay can be minutes or hours.

Observation of photoluminescence at a certain energy can be viewed as an indication that an electron transitioned between states separated by this transition energy. While this is generally true in atoms and similar systems, correlations and other more complex phenomena also act as sources for photoluminescence in many-body systems such as semiconductors or metals. A theoretical approach to handle this is given by the semiconductor luminescence equations.