Phosphorescence
Phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. This is in some cases the mechanism used for "glow-in-the-dark" materials which are "charged" by exposure to light. Unlike the relatively fast reactions in a common fluorescent tube, phosphorescent materials used for these materials absorb the energy and "store" it for a longer time as the processes required to re-emit the light occur less often.
Phosphorescence Media
Phosphorescent bird figure
After an electron absorbs a photon of high energy, it may undergo vibrational relaxations and intersystem crossing to another spin state. Again the system relaxes vibrationally in the new spin state and eventually emits light by phosphorescence.
An electron microscope reveals vacancy defects in a crystalline lattice of molybdenum disulfide. The missing sulfur atoms leave dangling bonds between the molybdenum atoms, creating traps in the empty spaces.
Phosphorescent elements of a wrist watch that had been exposed to bright light: clock face with twelve dots as well as minute and hour hand
Zinc sulfide (left) and strontium aluminate (right), in visible light, in darkness, and after 4 minutes in the dark.
Calcium sulfide (left) and metal-earth silicate (right) phosphoresce in red and blue respectively.
Before image of capturing a shadow on a phosphorescent wall.
