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Strong force?

  1. Jan 7, 2006 #1
    I was wondering, and it baffles me, how is the strong force involved in radioactive decay? I know ecxatly how the weak force is involved but thats about it.
  2. jcsd
  3. Jan 7, 2006 #2
    The strong force has nothing to do with radioactivity, at least not directly. The strong force binds quarks together through the exchange of gluons. This gluon-exchange is caracterized by the fact that all colours (ie the quantumnumbers associated with the strong force) involved must add up to yield the neutral colour, white. The strong force, of which the strength is described by asymptotic freedom, binds :

    1) three quarks to form baryons : eg protons, neutrons
    2) quark-anti quarks to form mesons : eg pions.

    The atomic nucleus is held together by the residual strong force, mediated by pions (these are the lightest mesons), which denotes the attractive interaction between the constituent quarks of several different baryons.

    Radioactivity is described by the weak force, through the change of the quark flavourquantumnumber.

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  4. Jan 7, 2006 #3


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    (The following is a somewhat simplified description).

    Alpha (He4 nucleus) decay results from a combination of em and strong force. Strong force holds nucleus together, while em tries to break it up. Alpha decay results when em wins.
  5. Jan 7, 2006 #4


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    'Radiation' is a bit of a dated concept in physics. Alpha decay proceeds as explained above, beta decay is a weak force interaction and gamma decay is pure EM.
  6. Jan 8, 2006 #5
    An interesting question is whether or not the alpha [He4] is "preformed" within the atomic nucleus before this decay process, and how this may effect both em and strong force ?
  7. Jan 8, 2006 #6
    the distance between quarks is classically 0.6fm(meson), so em is almost only 1MeV there, which can be ignored when strong act. but the possibility makes the decay act.
    Last edited: Jan 9, 2006
  8. Jan 9, 2006 #7


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    Well the strong force is involved in radioactivity, at least peripherally. In order to decay, an atom has to have energy available to decay with. To determine whether an atom has this or not, one had better take into account the strong force as it is the strong force that holds the nucleus together.

    As long as we're on the subject, it turns out that the E&M force is also involved in radioactivity, in particular, the 1S wave states of the orbital electron contributes to inverse beta decay. If you fully ionize an atom that is subject to inverse beta decay, the absence of the 1S electron will decrease the decay rate and lengthen the lifetime.

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