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B Why do metastable states in atoms exist?

  1. Nov 20, 2018 #1
    Hi
    My question relates to existence of metastable states in atoms which help out laser production. Is there any physical reason why some orbits allow electrons to stay for comparatively longer time 10-3 s than others which allow only 10-8s?
    Is this stay time same for all materials?
    Please guide.
     
  2. jcsd
  3. Nov 20, 2018 #2

    Drakkith

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    I believe the reason is related to the underlying physics governing the transition between energy states, known as selection rules.
    It's quite complicated and I don't know if there is an easy way to explain it. Perhaps someone more knowledgeable in this area can expand on this.
     
  4. Nov 21, 2018 #3

    DrDu

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    Drakkith is right. The most common reason for metastable states in atoms (or molecules) is due to the metastable state having different spin than the ground state. Often, the ground state is a singlet (i.e. the spins of the electrons are all paired up) while some long-living excited state is a triplet state (i.e. the spin of two electrons is oriented parallel). As the coupling of the spin to orbital momentum is a relativistic effect, it is quite small, at least in lighter atoms.
     
  5. Nov 22, 2018 #4
    Thanks indeed. That sound interesting. I need to study it more.
     
  6. Dec 8, 2018 at 3:31 PM #5
    In a triplet, the unpaired excited electron has the same spin orientation as the unpaired ground electron, so it has to spin flip to get back down. This has a very low probability of occurring which makes the triplet state of let's say neon, for instance, metastable.
     
  7. Dec 9, 2018 at 11:12 AM #6
    Marisa5 Thanks indeed for this further help. This all helped me a lot. Great forum, great people.
     
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