Method of generating excited states
① Light excitation. Atoms or molecules in the ground state absorb a certain amount of photons and can transition to an excited state. This is the most important way to generate an excited state.
② Discharge. It is mainly used to excite atoms, such as high-pressure mercury lamps and xenon arc lamps.
③ Chemical activation. Certain exothermic chemical reactions may cause electrons to be excited, resulting in chemiluminescence.