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My understanding is that fluorescence occurs when light has sufficient energy to excite an electron, which then emits a different photon (always with a larger wavelength) and releases the energy it just absorbed. I have found plenty of materials that absorb UV wavelengths and emit visible wavelengths nothing really outside this range.

My question is, is there a limit on the wavelength that can be emitted or is it possible to have a material that absorbs infrared wavelengths and emits either far IR or microwaves and are there any materials that do so? To put it another way, is there a limit at which a photon of a long enough wavelength no longer has enough energy to excite an electron?

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There is no theoretical restraint that limits but the material that absorbs the photons should have energy levels that allow for this and for the release of lower-energy atoms.

See the attached image below i drew for you, the bandgap is lower for the third frequency generation, thus it has a longer wavelength. The first photon that comes in has the highest frequency since it excites the electron over a wider bandgap. The second frequency transition does not have to radiate a photon but can instead be phonons inside the material, and thus in this case we'd only have one photon in and one photon out of longer wavelength (lower frequency) .

enter image description here

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