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Mar8-12, 04:02 PM
P: 628
Quote Quote by mathman View Post
An electron in a higher energy state can simply emit a photon and drop down (spontaneous emission) or can be stimulated by a photon of the same wavelength as the transition (stimulated emission - the basic principle of lasers).
Sorry, I did not mean to imply otherwise [that a spontaneous emission could not occur].

I don't know enough about quantum physics to judge if it 'simply' emits a photon, or comment on when/how quick and excited electron 'chooses' to return to a lower state without external stimulus.