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B Life of free electrons in space

  1. Aug 28, 2016 #1
    If I shoot some free electrons detached from any atom in space from a space station what happens to the electrons? I know around the atom's nucleus electron creates cloud like movement having various energy levels. But what type of movement , cloud and energy the electron holds in absence of any atom nucleus in space ? Does it move like EM wave or does it emits photons which move as EM wave? What about energy movement of electron from/to upper/lower energy level which is required to emit photons ? What may be the future fate of these electrons?

    I was observing the movement of my ceiling fan which has 3 blades. Although I know it has three blades while rotating its not possible to know. Even if it has only one blade when rotating very fast we cannot guess the blade qty. It may be slightly analogy with electron cloud. When I hit the fan with something strongly only then I have some info about its nature, only then I know exact position of the blade. Else the single blade is all over the circle area at the same time. Not correct. Because of the limitation of our eyes which can't differentiate object if shown movement 10 frames in a second the fan seemed like a round plate. .

    See the video of CD shattering recorded in slow motion by slow mo guys:

    Although the CD is rotating at very high speed using speedy camera they captured CD as like it is not rotating (at 4:44 moment ). For electron we need both high speed camera and electron microscope. Then we may view the electron when in still. I know its not possible and is quantum mechanically wrong but I like to dream to view electron in such still state as like the CD in near or distant future.
    Last edited: Aug 28, 2016
  2. jcsd
  3. Aug 28, 2016 #2


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    Staff: Mentor

    To a very good approximation, you can ignore quantum mechanics in your electron beam. The electrons will move like classical particles until they hit something. If the electrons are very high-energetic, inverse compton scattering with light can become relevant. If they fly through a strong magnetic field, synchrotron radiation might become relevant.

    No, not at all. Such a model cannot reproduce the observations.
    No one can stop you if you want to use wrong models that lead to various misconceptions...
  4. Aug 28, 2016 #3


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    Staff: Mentor

    There are a number of misconceptions and misunderstanding here. In no particular order:
    1) The idea of the electron in a cloud-like movement around the nucleus isn't quite right. It's a better picture than the old one in which the electron is orbiting the nucleus like a planet, but it's still an oversimplification for people who haven't yet learned the real thing (Google for "schrodinger equation hydrogen" to get started on that).
    2) Most photon emission is not the result of electrons changing energy levels. The easiest way to see this is to consider the electromagnetic radiation emitted by a black body (or the filament of an incandescent light, or a glowing coal, or ....) - it looks nothing like the sharp peaks at particular frequencies you'd get if it were from electrons changing orbital energy levels.

    You find the behavior of free electrons the same way that you find the behavior of bound electrons around a nucleus: Solve Schrodinger's equation, and the difference comes in because the potential (the ##V(x)## term in the equation) is different in the two cases. However, this difference makes a very big difference in the form of the solution. In one case, you get bound electrons with stable states separated by discrete energy levels. In the other case, you get electrons that behave very much like classical particles; within the limits allowed by the uncertainty principle you can say that they're at a particular place at a particular time and moving in some specific direction with some specific speed. Your beam of free electrons is covered by the second case.
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