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What causes an electron to return to its ground state?

  1. Jan 25, 2014 #1
    I've recently realized I have completely taken for granted that electrons simply tend to be found in their ground state. I want to understand fundamentally what is causing the electron to drop back to its ground state. It feels a force from the positively charged nucleus, but if it was given exactly enough energy to hop up into an excited state, how does it lose that energy and consequently get forced back "down"?
  2. jcsd
  3. Jan 25, 2014 #2


    Staff: Mentor

    Its the process of spontaneous emission which requires QED to explain:
    'In quantum electrodynamics (or QED), the electromagnetic field has a ground state, the QED vacuum, which can mix with the excited stationary states of the atom (for more information, see Ref. [2]). As a result of this interaction, the "stationary state" of the atom is no longer a true eigenstate of the combined system of the atom plus electromagnetic field. In particular, the electron transition from the excited state to the electronic ground state mixes with the transition of the electromagnetic field from the ground state to an excited state, a field state with one photon in it. Spontaneous emission in free space depends upon vacuum fluctuations to get started.'

  4. Jan 25, 2014 #3
    Thanks Bill. Looks like this will have to wait for grad school!
  5. Jan 25, 2014 #4
    Bill, since you're so helpful, in a kind of related question.

    I'm reading about all of those transitions, lymann, balmer, paschen, and more.
    Everytime I look it up it always begins with: "in the hydrogen emmison spectrum..."

    Are these names only for hydrogen? What about the other elements? Do they have different names?
  6. Jan 26, 2014 #5


    Staff: Mentor

    This is more physical chemistry stuff - I am more of the mathematical physics bent.

    But all the above are for Hydrogen atoms and are the only ones I know of - and even then I had to look up paschen. They certainly exist, but its not something I am into.

    Sorry mate - must leave it up to someone else.

  7. Jan 26, 2014 #6


    User Avatar
    Science Advisor
    Homework Helper

    Only the H-atom can be fully solved in QM, since it's a 2-particle system. For the other atoms, you can't fully solve the spectral problem of the Hamiltonian, hence you can't determine the emission spectrum theoretically => the name of the transitions are only for the H-atom.
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