1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can an electron move to a higher energy level on a permanent basis?

  1. Mar 7, 2012 #1
    Hi, I have some very basic questions regarding electron energy levels/states.

    In the basic atom model when an electron becomes excited (i.e. absorbs a photon or collides with a nearby atom or particle) and moves into an energy state greater than its ground state, must it always eventually return to the ground state? Or are there circumstances where an electron may remain in this higher energy state on a permanent basis?

    Likewise, is it possible for an electron to drop to a lower state (i.e. after emission of a photon) on a permanent basis, or must it always return to its ground state?

    Any clarification would be very much appreciated.
     
  2. jcsd
  3. Mar 7, 2012 #2

    mathman

    User Avatar
    Science Advisor
    Gold Member

    The simple answer to your question is that there is no mechanism (except by outside intervention) to lock an electron into a particular excited state. Even the ground state is hard to maintain.
     
  4. Mar 7, 2012 #3
    Thanks. I guess what I was trying to ascertain was: Is the return to ground state inevitable? My current understanding is that the ground state is almost a 'default' energy level to which the electron, over a long enough time frame, will always return (unless it escapes the system). Or am I picturing this incorrectly?

    Excuse my lack of knowledge - am not a physicist, as you may have guessed...
     
  5. Mar 8, 2012 #4
    the ground state is the lowest energy state so it will always tend to end up there.

    even if it were below the ground state it would be in a higher energy state and would return to the ground state.
     
  6. Mar 8, 2012 #5
    Hi memphisforest,

    The answer to your question, is no. Its impossible for electrons to stay in any single energy state for a long time. (By long time i mean less that 1/1000000000 of a second.) You know that electrons continuously emit radiations of different frequencies or energies. This is due to the fact that they keep switching between different energy states. Though the Ground State is the most stable state for an electron, as Mathman put it well, it is difficult for an electron to stay in its ground state for a long time!

    Keep asking questions,

    Regards,
    math_way
     
  7. Mar 8, 2012 #6
  8. Mar 8, 2012 #7

    cmb

    User Avatar

    I don't believe what has been said in this thread.

    As far as my simplistic, 'classic' understanding goes, electrons require energy input to change orbital. That energy can't come from simply nowhere. Similarly, an electron in a higher orbital exposed to EM will drop down if exposed to further radiation of a similar wavelength as the transition represents.
     
  9. Mar 8, 2012 #8

    mathman

    User Avatar
    Science Advisor
    Gold Member

    An electron in a higher energy state can simply emit a photon and drop down (spontaneous emission) or can be stimulated by a photon of the same wavelength as the transition (stimulated emission - the basic principle of lasers).
     
  10. Mar 8, 2012 #9

    cmb

    User Avatar

    []

    EDITED/Deleted... sorry, wrongly attributed a statement to mathman instead of math_way
     
  11. Mar 8, 2012 #10

    cmb

    User Avatar

    Sorry, I did not mean to imply otherwise [that a spontaneous emission could not occur].

    I don't know enough about quantum physics to judge if it 'simply' emits a photon, or comment on when/how quick and excited electron 'chooses' to return to a lower state without external stimulus.
     
  12. Mar 9, 2012 #11
  13. Mar 9, 2012 #12
    Sure it can:
    Quantum mechanics, in fact, guarantees 'energy from no where'.
     
  14. Mar 9, 2012 #13

    cmb

    User Avatar

    OK, so, how often? Are you going to go along with math_way at once every nanosecond per atom?!!
     
  15. Mar 9, 2012 #14
    Hi,

    See, transition taking place once every nanosecond, is just a very rough estimate. It might infact take even lesser time, before a transition takes place, or even greater amount of time. The problem really is that in quantum mechanics, there can be energy energy changes at any pt in time, thereby triggering a transition. Hence transitions can take place at any point in time, and maybe in even less than a nanosecond.

    https://www.physicsforums.com/showthread.php?t=75192

    regards,
    math_way
     
  16. Mar 9, 2012 #15
    i think this is incorrect, correct me if im wrong but very rarely is there enough energy to excite a core electron to a non-ground state due to not only the immense energies involved in the n=1 to n=2 transition (tens to thousands of eV) but also the Pauli exclusion principle forbids inner electrons in most multielectron atoms from jumping to the lowest avaliable non-ground states. the potential well to escape is very very large.

    for OP, the electron will spontaneously fall back down because the high energy state is an unstable equilibrium and even the tinest perturbation will make it fall back down to the lower states. it might not directly fall down to the absolute ground state though; it could first lose energy through internal conversion and then radiate, which causes fluorescence.
     
  17. Mar 10, 2012 #16

    cmb

    User Avatar

    And would these transitions release EM radiation, or otherwise what are the conditions when EM is release, and when is it not released?

    Would you agree that EM is released and radiates when an electron undergoes a drop to a lower excitation state?
     
  18. Mar 10, 2012 #17
    all atoms and molecules have not only electronic energy levels but also vibrational and rotational energy levels superimposed on them. an atom can undergo a drop from one vibrational level to another in the same electronic energy state and release no radiation; this is called internal conversion. the excess energy is released as heat. of course then it will indeed drop down later to the ground state, but the EM radiation would be a lower frequency.
     
  19. Mar 10, 2012 #18

    cmb

    User Avatar

    It's a specific question for math_way. What he is saying does not add up, so I just want to probe his understanding of this.
     
  20. Mar 10, 2012 #19
    >>@cmb


    okay cmb, now put forward your question. My answer to the original question: Can an electron move to a higher energy level on a permanent basis?, is no. Its impossible to stay at a higher energy level permanently, given that:

    1) Electrons are most stable in their ground state
    2) And transitions can take place at any time, which means, it again is impossible for an electron, to stay in the same energy level, for a long time.

    These two are very basic assumptions. (High School Physics)

    I agree i got a bit off the topic, and started talking too much about transitions, but anyway go ahead and question me, if you really want to probe my knowledge on this topic. And go on, oppose me if you feel i am wrong

    regards,
    math_way
     
  21. Mar 10, 2012 #20

    cmb

    User Avatar

    I want you to clarify what you mean by suggesting electrons are constantly, and rapidly, bouncing up and down in their orbits. Why would this process not be emitting copious EM emissions?

    I think you have confused 'quantum fluctuations' with 'electron orbit' changes. I do not have background on quantum stuff, but even my classic knowledge says this is wrong. If an electron were to be in a metastable higher orbit then, yeah sure, constant quantum fluctuations may be at work to dislodge it from its orbit and send it hurtling back to its ground state.

    But I do not, at all, see that quantum fluctuations are capable of dislodging a ground state electron and shifting it up to a higher orbital, except in extremely rare statistically anomalous events (as in - once per megayear, or whatever..).

    So I want you to think about whether you've wrongly conflated quantum fluctuations with electron orbital changes.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Can an electron move to a higher energy level on a permanent basis?
Loading...