What luminescent effect is produced when a material continues to glow even after the radiant energy is turned off?

Answer 1

materials that "glow" absorb energy. Then usually the undergo a process called internal conversion to a lower excited state (S1). Usually this small drop in energy is dissipated through vibrations, etc...

The material then has to drop to the ground state (S0). There are a variety of ways the material can do this. The way that the particle can do this by emitting light is called fluorescence. Typically this happens within a few nanoseconds.

Note that a variety of input energy excitations all produce a single energy light (a very specific color), namely, the color corresponding to the difference between S0 and S1.

Fluorescence has a variety of scientific applications and is widely used in physics today.

A less useful but probably more popular form of glowing is phosphorescence. It is basically the same thing but because the S1 to S0 transition is "forbidden" it takes a long time to occur, thus it may emit the photon an hour later. This leads to a glowing effect.

Because of the larger time scales, it does not give the necessary time resolution required for most scientific experiments. If you were watching a fluorescent dot moving in a fluid, it would light up every few nanoseconds (if u continuously excited it), however, a phosphorescent one would light up every few hours, so for hours you will have no idea where it is.