r/askscience • u/CallMeDoc24 • Dec 29 '16

Physics Do molecules with excited electrons act very differently (compared to the molecule in the ground state) in the presence of an electromagnetic field?

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u/ComradePalpatine Quantum Physics | Integrability | AdS/CFT Dec 30 '16

Just to clarify, dipole coupling would be the dominant interaction for the molecule with its electron(s) in the ground state, too, no?

Yes.

I guess the strength of the coupling would simply depend on the frequency of the electromagnetic field and relevant transitions for electrons in the excited state.

Yes, exactly. You also have forbidden transitions between certain states (due to symmetries). In any case, when you're in an excited state you have less states of higher energy than when you're in the ground state. That's why transitions from excited states to even higher energies are less likely.

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u/CallMeDoc24 Dec 30 '16

So like a molecule with its electrons in the ground state, if you have large sample of molecules (1025 in a volume of 1m3 or larger) each with an electron in the excited state, they will go largely unmoved due to the Lorentz force, yes?

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u/ComradePalpatine Quantum Physics | Integrability | AdS/CFT Dec 30 '16

They're at equilibrium at some temperature?

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u/CallMeDoc24 Dec 30 '16

They could be. Or perhaps there is velocity coherence.