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Helium energy diagram

  1. Apr 10, 2009 #1
    I'm trying to have a guest on the neutral Helium energy level diagram using the Bohr theory approach (just with n, does not include 2nd quantum number or spin). I think it should give me a close result. If not, I have to understand why. I went to NIST website:
    And see the energy level for He I (neutral He) and H I (neutral Hydrogen) in the unit of eV. I discover something: The energy level of Helium is just energy level of Hydrogen plus 10 eV. My hypothesis is that this extra energy comes from the repulsion energy between the 2 electrons of Helium when one in excited state and one in ground state.
    My approach is to use the Bohr radius.
    For the ground state one (n=1), it would be a radius with one electron seeing 2 positive charge on the inside, so it would be the same as with radius of a ground-state-electron-of-a-singly-ionized-Helium (He II).
    For the excited one in n=2, it would see the inside as 1 positive charge (because the ground state electron cancel one charge) and have the same radius as with the n=2 electron in Hydrogen of Bohr.
    I calculated the difference between the 2 radius, use the Coulomb equation to get the repulsion energy, and the repulsion come out as about 7.5 eV.
    So I say, this mean that to get to the ground state, the outside electron will have to overcome this much extra repulsion energy.
    Is my approach wrong? and I can't seem to explain why the experimental energy of NIST is higher than mine, and my approach seems to me too simple. Maybe it's just a coincidence that my result get close.
    Could someone please help me...? Thank you very much!!!
  2. jcsd
  3. Apr 12, 2009 #2
    I notice you've been posting questions about Helium recently. I'm sorry you haven't been getting much of a response. I especially found the NIST website to be interesting.

    The thing I like about your questions is that your are attempting to do actual physics, namely calculate energy levels of specific atoms. Rather than asking general philosophical questions about things like Many Worlds or the Double Slit experiment. Unfortunately, I can't really encourage you in any attempt to apply the Bohr methods to the Helium atom because I don't believe this line of thinking is productive in any way. But at least I found your information thought-provoking.
  4. Apr 12, 2009 #3
    Oh...thank you ^^
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