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Heavy Atoms

  1. Oct 15, 2009 #1
    A hydrogen atom is consists of a proton (uud quarks) and an electron.

    Is there a heavier atom of hydrogen that consists of a type of proton (ccs or ttb quarks) and a muon or tauon respectively?

    Are these
  2. jcsd
  3. Oct 15, 2009 #2


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    To my knowledge, no nucleons based on combinations (ccs or ttb quarks) have been produced in this part of the universe. Muons don't exist long enough to produce an atom that could be investigated.
  4. Oct 15, 2009 #3
    ccs has never been observed, and it would be extremely short lived. ttb does not exist, because top quark is too unstable to form composite particles.

    It is possible to form an "atom" out of a proton and a muon. It would only last a couple of microseconds before muon decays.
  5. Oct 15, 2009 #4

    Vanadium 50

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    True, although there are "hypernuclei", where one of the nucleons has been replaced by a hyperon, most often a [itex]\Lambda^0[/itex], but a[itex]\Sigma[/itex] hypernuclei have also been produced and studied. There are people who dedicate their entire careers to the study of hypernuclei.

    This field has some surprises: [itex]{\rm ^5_{\Lambda}He}[/itex] should look a lot like [itex]{\rm ^4He}[/itex], but in fact, unlike the alpha particle, is not very tightly bound at all.

    The problem with (css) is that it's pretty much at our limit of abilities to produce a hypernucleus with one strange quark, let alone two, let alone charm. But this is a practical problem, not a fundamental one.

    That's not the case. A negative muon can be captured by a nucleus, and it can live long enough to undergo atomic transitions, giving off x-rays as it de-excites. These mu-mesic x-rays (as they were called when they were discovered by Val Fitch and Jim Rainwater in the early 1950's) provide a lot of information on the charge distribution of the nucleus - because a muon is 200x heavier than an electron, it's Bohr radius is 200 times smaller, so the effect of the nuclear charge distribution (e.g. quadrupole deformations) is orders of magnitude larger.

    Indeed, the lifetime of the muon is about 20 trillion times longer than the classical orbit period. Microseconds seems like a short time to us, but compared to typical atomic transition times, it's huge.
  6. Oct 15, 2009 #5
    Muonic hydrogen (proton plus negative muon) has been made in the laboratory, and its atomic transition energies have been measured. The binding energy of the muon is about (105.658/0.511) times 13.6 eV*. The bound muon does not interact with the proton**, and decays while in the ground state of the muonic hydrogen atom.
    Bob S
    * does not include significant reduced mass correction.
    ** protons do absorb muons in high-Z atoms.
    Last edited: Oct 16, 2009
  7. Oct 16, 2009 #6
    Hi bob, If the muon decays whilst in the ground state where does the energy come from to keep the atom in the ground state
  8. Oct 16, 2009 #7
    Is the energy of the x-ray equal to the transition from muon to electron or is there some energy taken from the nucleus..as in ccs to uud
  9. Oct 16, 2009 #8

    Vanadium 50

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    Neither. It's an ordinary atomic transition.
  10. Oct 16, 2009 #9
    In muonic hydrogen, the muon cascades down to the 1S state in a few picoseconds, and usually decays into a muon neutrino, an electron anti-neutrino, and a high energy electron (up to 52 MeV), leaving a free proton to find a free electron. The muon absorption rate in nuclei varies as Z4, and in high Z nuclei the muon spends most of its time in nuclear matter, and is captured by a proton in 60-80 nanoseconds, decaying to a neutron and a muon neutrino.
    Bob S

    [added] muon lifetime is about 2.2 microseconds.
    Last edited: Oct 16, 2009
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