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Nature of electrons, the 'wavicle'.

  1. Feb 3, 2004 #1
    At the quantum scale physics becomes hugely unpredictable and particles appear to defy the laws of physics at every turn, only obeying classical physics on 'average'.

    Beta rays appear to have wave like properties, they consist of electrons, which are known to have a mass and have particle like properties. So electrons are known as wavicles.

    I am trying to understand how electrons act when they orbit an atom, in particular how heat energy causes electrons to 'jump' to higher principle energy levels, become unstable, 'fall' back down and release EM radiation. How does the kinetic soup of vibrating atoms cause the electron to become displaced? Why does an electron 'jump' when only a certain amount of energy has been applied to it?

    My previous idea of an atom is a very small particle nucleus at the center with a large and rigid orbitting wall of electrons compared to the size of the nucleus. This idea of an atom obviously does not apply to the quantum world. I believe that to help understand how heat causes electrons to 'jump', I need to get a better idea of how electrons act at the quantum scale.

    What are the properties of electrons in orbit around an atom?
     
  2. jcsd
  3. Feb 3, 2004 #2
    I've always wondered the same thing

    I always thought to absorb radiation you had to have an electric dipole moment to couple the states of definite energy (the perturbation term). Now I'm pretty sure you aren't inducing electron transistions when you heat something, because thermal radiation (infrared) has too low of an energy. Instead you're exciting the vibrational and rotational modes of the molecule, which means those modes have to have an electric dipole moment, which I don't understand.

    Also I know that you don't have to get a photon with exactly the right energy to induce a transition - you just have to be fairly close. If this happens does the atom go into a state that's a superposition of the energy level you were initially at and the energy level you were trying to get to (such that the expected energy equals the energy of the photon)? And the atom won't stay in that mixed state forever - when it drops does it emit a photon of the expected energy, and if not, how is energy conserved?

    All right, those are my questions. I'll try to answer yours now (no promises though :p):


    How does the kinetic soup of vibrating atoms cause the electron to become displaced? Why does an electron 'jump' when only a certain amount of energy has been applied to it?

    I've no idea. Thermodynamics says when you have a bunch of energy and decide which part of the system gets what part of the energy, that all possibilities are equal. Therefore it's possible, although unlikely, that vibrating atoms would cause electron transitions, because electron transitions have higher energy, which means less energy to divide amongst everyone else. I don't know the actual quantum mechanism that does this (like I stated above).

    What are the properties of electrons in orbit around an atom?

    Any state can be represented as a linear combination of the "energy+total angular momentum+angular momentum along z-axis+spin" eigenfunctions (actually this is only for the hydrogen atom). The electron can't fall into the nucleus because of the uncertainty principle. The electron is bound because of its attraction to the nucleus. The maximal description of the hydrogen atom is those 4 quantum numbers I listed above (I'm assuming the hydrogen atom is stationary). I don't think the electron radiates energy clasically - only when they make a transistion to another energy level.
     
  4. Feb 3, 2004 #3

    HallsofIvy

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    I'm concerned about your assertion that "heat energy causes electrons to 'jump' to higher principle energy levels". How would one even define "heat" in a quantum situation?
     
  5. Feb 3, 2004 #4
    That's another thing I don't know. If you paint an object black and heat it up to around 5800 K, then your object will radiate light. Now I'm trying to recall how the blackbody model was derived. It seems to that it doesn't matter what the material is, so long as there are atoms to absorb any frequency. There can be many types of atoms that'll absorb a particular frequency (and each type with a different amplitude) - it doesn't matter, so long as there's just one type of atom, because at constant temperature each type has to be in equilibrium with the radiation in the box. I don't know the exact mechanism that causes heat to cause electron energy jumps - as far as I'm aware I've only been exposed to photons causing transitions between energy levels. However, presumably in the vibrational modes there can be transistions to a lower energy level causing photon emission. I've got how the statistics of bosons determines the blackbody spectrum, but the actual mechanism that's going on (vibrational modes, electron transitions) I'm at a loss to explain.
     
  6. Feb 4, 2004 #5
    Thankyou redX, though the question remains. What processes are involved during the transfer of energy from heat energy to the election?


    "I'm concerned about your assertion that "heat energy causes electrons to 'jump' to higher principle energy levels". How would one even define "heat" in a quantum situation?"

    There is something called 'thermodynamics', which I suggest you find out more about. I'm sure you have heard about the vibration theory of atoms and how heat is a measure of violently atoms are vibrating. Just imagine atoms as negatively charged magnets which are in motion forwards and backwards, over and over again. Hopefully you already know of potential energy. The 'speed' and pressure at which these atoms vibrate is proportional to the internal energy of the system.
     
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