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Energy radiated by an electron

  1. Dec 15, 2011 #1
    Do electrons really move around the nucleus in an orbit? Or we cannot say that because of quantum rules which say that we can only locate a electron at a position with certain probability? If it does revolve, then:

    1) where is the energy coming to make the electron go around the nucleus?
    2) if electron revolves, and since it is a charge particle, it will create magnetic field and in effect will eventually radiate with certain energy? How long can it really last?
     
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  3. Dec 15, 2011 #2

    Drakkith

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    No, they do not occupy an orbit like a planet does around a star. The correct term is an "orbital". Each electron can only occupy a certain energy state. In this state the electron has a probability of being found in certain locations. The electron cannot "fall" down into the nucleus because it isn't actually moving around it.
     
  4. Dec 15, 2011 #3
    ???

    "If we assume for example that the electrons in the atom are stationary, there exists no stable arrangement of the electrons which would preven the electrons from falling into the nuclues under the influence of coulomb attraction"

    Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles pp. 95

    I thought zero point energy kept the electron from collapsing into the nucleus.
     
  5. Dec 15, 2011 #4
    Thanks, that helps.

    So, when an electron jumps to a lower energy orbit, why does it radiate energy in electromagnetic waves?
     
  6. Dec 15, 2011 #5

    Drakkith

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    From my understanding the electrons wavefunction gives it a range of areas it can occupy yet doesn't require it to actually move around the nucleus. Additionally electrons can only occupy energy levels that adhere to specific rules. They can't collapse because that would require them to merge with protons to form neutrons, and that requires energy.
     
  7. Dec 15, 2011 #6

    Drakkith

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    The difference in energy between the two levels is given off as EM radiation. Without losing energy the electron could not occupy the lower energy level. There simply isn't another way for it to lose energy other than EM radiation as far as I know, though I'm not 100% sure on that.
     
  8. Dec 15, 2011 #7
    Its my understanding that electrons have to mantain a physical energy to stay in that energy level, when they jump, the frequency of the EM radiation released is equal to the energy of the photon divided by planks constant. So it obeys classical theory in this sense. Bohr believed electrons didn't release EM energy when orbiting, but I assumed when they mentioned zero-point energy later in the book, that this was the electron abrsorbed energy keeping it from colliding with the atom, hence the energy released orbiting, was equal to the energy absorbed through ZPE keeping it from colliding, but I haven't checked this yet and it's been a year sense I've taken modern physics.
     
  9. Dec 15, 2011 #8

    Drakkith

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    I'm not sure what you mean by "maintain a physical energy". Each level has its own unique amount of energy that an electron has while it occupies it. This requires nothing to maintain.

    Bohr's orignal model of the atom was incomplete and it required full Quantum Mechanics to explain why electrons did not radiate energy as they orbit the nucleus. The answer was that they don't orbit and don't radiate energy.

    Zero point energy is simply the lowest energy state of a system I believe. It is not a source of energy to my knowledge. Electrons most definately do not constantly radiate energy when they are in their orbital.
     
  10. Dec 15, 2011 #9
    By physical energy I mean

    "Since the atomic electron must have a total energy exactly equal to the energy of one of the allowed energy states, the atom can only absorb discrete amounts of energy from the incedent electromagnetic radiation"

    Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles pp. 103

    I think ZPE is based more on the heisenburg uncertainty principle that since you can never know the simultanous position and momentum of an electron it is always moving.

    Some people believe that ZPE is absorbed through vacum energy. Vacuum energy relies on background radiation from virtual particles, which is based on pertubation theory. Pertubation theory goes back to the heisenburg uncertianty principle.
     
  11. Dec 15, 2011 #10

    Drakkith

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    From wikipedia:

    Since this is the ground state, the minimum energy state, there is no energy available for work. It is not a source of energy able to be absorbed to my knowledge.

    Yes, that is correct.
     
  12. Dec 15, 2011 #11
    If ZPE is source of energy, thats something that is still being debated since it relies on vacuum energy which still encounters controversy.
     
  13. Dec 15, 2011 #12

    Drakkith

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    To my knowledge it does not encounter controversy in real science, only in psuedoscience and with people who claim to make free energy machines. Zero point energy is very well defined by Quantum Mechanics.
     
  14. Dec 15, 2011 #13
    "The theory considers vacuum to implicitly have the same properties as a particle, such as spin or polarization in the case of light, energy, and so on. According to the theory, most of these properties cancel out on average leaving the vacuum empty in the literal sense of the word. One important exception, however, is the vacuum energy or the vacuum expectation value of the energy. The quantization of a simple harmonic oscillator requires the lowest possible energy, or zero-point energy of such an oscillator to be:


    Summing over all possible oscillators at all points in space gives an infinite quantity. To remove this infinity, one may argue that only differences in energy are physically measurable, much as the concept of potential energy has been treated in classical mechanics for centuries. This argument is the underpinning of the theory of renormalization. In all practical calculations, this is how the infinity is handled."

    http://en.wikipedia.org/wiki/Vacuum_energy

    When feynman discusses the renormalization factor, he refers to it as as magic, becuase they simply put in zeros to make the equation work. To me, it still seams controversial.
     
  15. Dec 15, 2011 #14
    In any case:

    "Vacuum energy is the zero-point energy of all the fields in space, which in the Standard Model includes the electromagnetic field, other gauge fields, fermionic fields, and the Higgs field. It is the energy of the vacuum, which in quantum field theory is defined not as empty space but as the ground state of the fields. In cosmology, the vacuum energy is one possible explanation for the cosmological constant.[3] A related term is zero-point field, which is the lowest energy state of a particular field.[4]"

    http://en.wikipedia.org/wiki/Zero-point_energy

    "Vacuum energy is an underlying background energy that exists in space even when the space is devoid of matter (free space). The concept of vacuum energy has been deduced from the concept of virtual particles."

    http://en.wikipedia.org/wiki/Vacuum_energy

    My logic was that ZPE absorbs vacuum energy from the background radiation from virtual particles. How much is absorbed was determined from the renormalization factor which was made to match experiments.
     
  16. Dec 16, 2011 #15

    Drakkith

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    You cannot absorb energy from a minimum state. It cannot go any lower. And virtual particles would have to become real particles in order to give up any energy, which only happens in exceptional circumstances. Even in processes that may result in virtual particles becoming real, such as hawking radiation, the energy is not taken from the vacuum.
     
  17. Dec 16, 2011 #16
    Here's how I came to the conlusion, I stand to be corrected, but it still seems logical to me.

    "One of the most interesting aspects of vacuum energy (with or without mirrors) is that, calculated in quantum field theory, it is infinite! To some, this finding implies that the vacuum of space could be an enormous source of energy--called "zero point energy." "

    http://www.scientificamerican.com/article.cfm?id=what-is-the-casimir-effec

    "The Unruh temperature, derived by William Unruh in 1976, is the effective temperature experienced by a uniformly accelerating detector in a vacuum field."

    http://en.wikipedia.org/wiki/Unruh_effect

    Since the electron is accelerating around the atom (as orbiting bodies do), it would absorb vacuum energy due to the unruh effect.
     
  18. Dec 16, 2011 #17

    ZapperZ

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    Please read the FAQ sub-forum in the General Physics section.

    Zz.
     
  19. Dec 16, 2011 #18
    How does the electron "jump" from one energy state to another. Do they teleport or something (since the energy states is quantized)?
     
  20. Dec 16, 2011 #19

    Drakkith

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    They simply acquire more energy by absorbing a photon, getting hit by another atom, etc. (Or lose energy to jump down) The "jump" simply means they absorb or give up energy and must occupy another energy level.
     
  21. Dec 16, 2011 #20

    Drakkith

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    Yes, which is why renormalization is necessary. I don't think most people actually believe there is infinite energy, but more due to our own calculations. But that's just my opinion, I don't know for sure. From looking at zero point energy and related areas I simply don't see how you can get energy from a minimum energy state.
     
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