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Electron orbits, QM, Exclusion Principle and location

  1. Jan 11, 2007 #1
    I remember that electrons exist in the probability cloud that corresponds to the orbital they reside in, and according to the Pauli Exclusion Principle, they can't share spin in the same orbital.

    According to the Copenhagen interpretation of quantum mechanics, when the wavefunction is collapsed because the electron is observed, is it located near it's previous location the last time it was observed or is it anywhere in the probability cloud? I ask this because I thought the electron can be anywhere in the probability cloud, even despite having previously been observed to be in a specific point.

    So perhaps the electron appears at any random place at any time, right?

    o| Hiram
  2. jcsd
  3. Jan 12, 2007 #2


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    I'm not an expert in the field of QM. But it is clear that Measurement in QM is a very big and at times controversial subject. I would guess that the electron would be distributed according to its probability distribution and your previous measurement cannot tell you anything about your next.
  4. Jan 12, 2007 #3
    "So perhaps the electron appears at any random place at any time, right?"...maybe the uncertainty answer this question...now try the example of an electron going to a square potential barrier... there is a probability that the electron will be in other region after the barrier but it is a small probability and if u take the electron over it , the probability is big of finding the electron in the 3rd region and so the transmission coefficient is higher then the reflected coefficeint now if the energy is equal the potential energy ...shroedinger's solution is linear now and so some things changes ... but for me i know there is a transmission coeff. but i am not getting to it ... i keep trying .... hope i helped in some way
  5. Jan 12, 2007 #4
    I think I understood part of it

    Let me clarify this: if the electron is in region 1, and goes near a square potential barrier, it might be found in region 2, on the other side of the barrier. If we take the part of the wavefunction that has crossed over, then sometime later it might be found in region 3, also on the other side of the square potential barrier and even farther away from region 1 than region 2?

    This would mean that the electron partially might moving consistently in that general direction. This does help me with my original question.

    Would part of the wavefunction still be found in region 1 when the wavefunction reaches region 3?

    o| Hiram
  6. Jan 12, 2007 #5
    yes absolutely ...because we have incident wave and reflected wave and tunneling wave and transmission wave ....
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