Phosphorus compounds are phosphorescent. They store light and give it off later.
Luminescence
There are three main forms of luminescence at play: fluorescence, phosphorescence and chemiluminescence. Fluorescence and phosphorescence are two forms of photoluminescence. In photoluminescence, a substance’s glow is triggered by light, in contrast to chemiluminescence, where a chemical reaction causes the glow.
Phosphorescence
Phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. Examples of phosphorescent materials include glow-in-the-dark stars, some safety signs, and glowing paint.
- In phosphorescence, light is absorbed by a material, bumping up the energy levels of electrons into an excited state.
- However, the energy of the light doesn’t quite match up with the energy of allowed excited states, so the absorbed photos get stuck in a triplet state.
- Transitions to a lower and more stable energy state take time, but when they occur, light is released. Because this release occurs slowly, a phosphorescent material appears to glow in the dark.
