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What makes something glow in the dark? The only explanation that I can come up with for what makes things glow in the dark is that there is probably a chemical reaction slowly releasing the light that was previously absorbed. Am I correct?

How does this phenomenon work?

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The glow in the dark phenomena is called luminescence. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. Three of the common mechanisms are:

  1. Fluorescence: Light is emitted during the excitation with invisible electromagnetic radiation.
  2. Chemoluminescence: A chemical reaction radiates energy in for of electromagnetic radiation (e.g. glow sticks, luziferase reaction,...)
  3. Phosphorescence: You can read about the quantum mechanical processes here. There is one interesting thing I want to point out. While the most phosphorescent materials are solid, in this paper, they have reported the synthesis and afterglow of water-soluble ZnS:Cu,Co nanoparticles.

I know Wikipedia is not at all a reference, but there you can find an overview of all types of luminescence.

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When a glow stick breaks, it breaks a thin glass barrier on the inside that allows two different substances to come into contact, mix and react. I am not sure of the exact reaction that occurs, but when chemical bonds are broken they can emit photons (light). In this case, the photons emitted are in the visible spectrum.

The case for glow in the dark stickers is a bit different. All things are absorbing and releasing photons constantly, but in most cases, the photons aren't in the visible spectrum. Glow in the dark things absorb visible light and then release the photons as visible light. This is unlike most other objects which may release them as a lower frequency instead and thus not be visible.

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  • $\begingroup$ so is it creating the chemical bonds when they absorb photons and destroying them again when it releases them? $\endgroup$
    – ruckus
    Aug 27, 2015 at 16:38
  • $\begingroup$ In this case, the photons are absorbed by the electrons of the atoms and it excites them into a higher orbit. However, electrons have a certain orbit that they are "most comfortable" and will try to stay there, also called the ground state. Soon after the electron absorbs the photon, it will release it to return to its ground state. Depending on the substance, it will release it at various wavelengths, not necessarily the same wavelength it absorbed it at. Hope this helped :) $\endgroup$
    – Ryan
    Aug 30, 2015 at 21:11
  • $\begingroup$ So the electrons release the light when they return to the valence shells? thanks! $\endgroup$
    – ruckus
    Aug 31, 2015 at 0:51
  • $\begingroup$ exactly so @vincentScalia $\endgroup$
    – Ryan
    Aug 31, 2015 at 0:59
  • $\begingroup$ "in most cases, the photons aren't in the visible spectrum": When you shine light on objects, they do reflect light - that is how we can see their colors. The key to glow in the dark stickers is that they absorb visible light and somehow store that energy, releasing even after the lights are turned off. $\endgroup$
    – Karsten
    May 20, 2019 at 16:02
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Reactions emits energy in different forms. Could be heat, light or electrical. If the form emited is light energy form it surely will glow irrespective of the external environmental characteristics in this case dark!

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