In laser we excite the atom from ground-state to excited-state, the atom then decay non-radioactively to metastable state and a population inversion produces as in He-Ne laser. My question is that is it possible that we directly excite the atom to metastable state and prouce the population-inversion in the metastable state without using excited state?
The advantage of this scheme is that less energy will then be required for pumping.
I think this is related to many reasons, the population inversion can not be achieved with the life time of the meta stable level according to rate equations
Based on quantum mechanics principles it is a lot easier to excite the atom to a higher level, relatively more stable, excited state than a metastable state. Additionally the ease of radationless transition from the higher excited state to the metastable state will also explain the reason to some extent.
Srini vasan
Metastable state is relatively more stable than excited state. If the excitation was based on stability of the state then the atom will certainly excite to metastable state but this is not the case.
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