We have stimulated emission and spontaneous emission. Do we also have stimulated absorption and spontaneous absorption?

We do have stimulated absorption where atoms absorb energy and move to the excited state when electromagnetic wave of suitable frequency is incident on it.

However, there is nothing called spontaneous absorption. This is because for absorption to take place electromagnetic radiation has to be incident. Absorption is not possible without any incident of radiation, as if there is no incident energy, there is nothing for the atoms to absorb.


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