In phosphorescence, energy is absorbed and then slowly released in the form of light. The slower time scale of the re-emission (as compared with fluorescence) is associated with "forbidden" energy state transitions. The light from phosphorescence may be released up to several hours after the exposure to the initial radiation.
Phosphorescence Example
By Anne Marie Helmenstine, Ph.D., About.com Guide
These photos illustrate phosphorescence. This is europium doped strontium silicate-aluminate oxide powder (cyan pigmented), under visible light, long-wave UV light, and in darkness.
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