PHOSPHORESCENCE

n. luminosity, quality of producing light after exposure to radiation

In common use, phosphorescence also refers to the emission of light by bioluminescent plankton, and some other forms of chemoluminescence. Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum mechanics. As these transitions occur less often in certain materials, absorbed radiation may be re-emitted at a lower intensity for up to several hours.
See more at Wikipedia.org...

Phos·pho·res·cence n. 1. Persistent emission of light following exposure to and removal of incident radiation. 2. [more]Phosphorescence - Community and Resources

Noun
1. a fluorescence that persists after the bombarding radiation has ceased
(hypernym) fluorescence
(derivation) phosphoresce

n. phosphorescence, luminosity, quality of producing light after exposure to radiation