How does phosphorence work? How can an object capture light and use it to glow for long periods?


How does phosphorence work? How can an object capture light and use it to glow for long periods?

In: Chemistry

Its not so much that the light is captured, but more the energy of the light. Basically, some atoms and molecules will have situations wherein an electron in the outer shell can, by exciting it with light, be moved into a higher orbit, if you will (Think of Bohrs nuclear model here, as thats really all you need to visualize this)
Now, most of the time, youll have those electrons move right back once there is no more light to excite it. However, in some cases, like phosphorus, the electron would, in order to do so, have to pass through what is called a forbidden state, which is basically a state that takes a lot of energy to reach and isnt very stable.
As the electron falls back down through this forbidden state, it releases the energy that had previously been stored in it, in the shape of visible light. However, since the odds of this happening for any individiual electron are low, this effect will keep going for quite some time.
Of course, this is only one possible mechanism. For example, there are also various nuts that are phosporescent. Peanuts for instance. I dont remember the precise mechanism, but theres a polymer (Polymer here referring to a long chain of small molecules, so called monomers, that link up to form a macromolecule) in peanuts and a lot of other nuts that will, when exposed to blue or ultraviolet light, start glowing blue, as that polymer is split up into its monomers by the light, which then reform the polymer, which then proceeds to release that same light again. (This works with fresh peanut butter as well in case you have a blacklight lamp and wanna try it out)

Tl;dr: In chemistry, some processes can be caused by light being absorbed by something. if that same process is reversible, reversing it causes the light to be released, as concepts like the conservation of energy demand that the energy has to go somewhere.

Light is an electromagnetic wave that you can percieve. It can be emitted in various ways, one of them is by breaking a molecule or having a molecule release its surplus of energy.

Phosphorence is the second case: when you light a molecule, it wil absorb certain photons and get “excited”. As soon as it is excited, it tries to get back to its “calm” state which means that it will have to lose energy. To do so, it will create a new photon (which is energy) and eject it with more or less energy (that will define its wavelenght).

To expand a bit more on “excited” molecules and “calm” molecules, a molecule have a shape/position that is the most comfortable for it which is its “calm” or “low energy” position (so the atoms are at the most efficient distance from each other, and the molecule is at the most efficient distance from the others). When you bring energy to it, it might elongate or retract the bound between two atoms or it might increase or decrease the distance between two unbounded atoms, which don’t want to be that far/close, so they will come back to their “comfortable” position by releasing the energy they stored.