I think a substance which emits light when it gets vaporized could have numerous applications, for example in display technology or in leakage detection.
The only problem is: I'm struggling to find a explanation how this should work.
Light emission from atoms stems from the electrons changing there discrete energy states inside the atom. On the other hand phase change is connected to inter-atom forces and thermo-dynamics. (This should apply to molecules as well).
Is there a phenomenon, which somehow connects these two mechanism, so that a phase change is always accompanied with photon emission? Or is there a material / compound / element with this property?
As photon emission is always also energy emission I'd suspect this is more likely when changing from solid to liquid or liquid to gaseous. Optical photons and (more-or-less) standard conditions would be preferable, but I'm mainly interested whether such thing exists or could exist at all.