Persistent luminescence
Commonly referred as phosphorescence, persistent luminescence is the phenomenon encountered in materials which make them glow in the dark after the end of an excitation with UV or visible light.
Mechanism
The mechanism underlying this phenomenon is not fully understood [1]. However, the phenomenon of persistent luminescence must not be mistaken with fluorescence and phosphorescence (see for definitions [2] and [3]). Indeed, in fluorescence, the lifetime of the excited state is in the order of a few ns and in phosphorescence, even if the lifetime of the emission can reach several seconds, the reason of the long emission is due to the desexcitation between two electronic states of differents spin multiplicity. For persistent luminescence, it has been known for a long time that the phenomenon involved energy traps (such as electron or hole trap) in a material [4] which are filled during the excitation. After the end of the excitation, the stored energy is gradually released to emitter centers which emit light usually by a fluorescence-like mechanism.
References
- ^ T. Aitasalo, P. Deren, J. Hölsä, H. Jungner, J.C. Krupa, M. Lastusaari, J. Legendziewicz, J. Niittykoski, and W. Strek. Persistent luminescence phenomena in materials doped with rare earth ions. J. Solid State Chem., 171 :114, 2003.
- ^ http://goldbook.iupac.org/F02453.html
- ^ http://goldbook.iupac.org/P04569.html
- ^ H.W. Leverenz. Luminescent solids (phosphors). Science, 109 :183–189, 1949.