Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why are there only limited modes of radioactivity?

  1. Jul 13, 2011 #1
    Most texts on radioactivity starts by saying "there are three important modes of radioactivity-alpha, beta and gamma......." and goes on to describe their properties. But why are there only a few modes of radioactivity? Does that mean the modes observed so far, or, are there theories to describe the possible modes? Putting it other way, when a new radioactive isotope is ever discovered, will the mode of radioactivity be confined to alpha, beta, gamma or neutron emissions?
     
  2. jcsd
  3. Jul 13, 2011 #2

    mathman

    User Avatar
    Science Advisor
    Gold Member

    The radioactive decay mode of every radionuclide is known. In addition to the three you mentioned, there are positron emission and electron capture (variations of beta decay) and spontaneous fission.
     
  4. Jul 13, 2011 #3

    Drakkith

    User Avatar

    Staff: Mentor

    There are limited decay modes because there are a limited amount of types of particles and forces. One can only exit a door a certain amount of ways!
     
  5. Jul 13, 2011 #4
    There is also a neutron radiation (accompanies spontaneous fission).

    Decay by proton emission is also possible, but it's more of theoretic interest: IIRC, all isotopes which exhibit it are very hard to produce, and very unstable.
     
  6. Jul 13, 2011 #5
    Electron capture per se is not a radiation, since captured electron is not radiated. But usually electron capture causes some gamma emission (because outer electrons fall into just-vacated inner orbital) and sometimes beta (auger electrons).

    There is another rare "non-radiating" type of beta-decay, when newly born electron goes into an empty orbital. This requires empty orbital, usually inner one, IOW: requires atom to be highly ionized.
    Interesting example is Dy-163: it is ordinarily stable, but when fully ionized (all 66 electrons stripped), it has half-life of only 47 days.
     
  7. Jul 14, 2011 #6
    Some physicists have tentatively made a recent correlation between the suns activity and slight variances in the decay rate of radioactive substances. If it turns out to be a good observation there will have to be new discoveries regarding radioactivity.
    http://physicsworld.com/cws/article/news/36108
     
  8. Jul 14, 2011 #7

    Drakkith

    User Avatar

    Staff: Mentor

    I wouldn't place any real trust in this yet.
     
    Last edited by a moderator: Apr 26, 2017
  9. Jul 14, 2011 #8

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    There are other modes of decay at higher energies. Very heavy nucleus can decay by carbon nucleus emission. Also more exotic things can happen at extreme energies in particle accelerators involving mesons and muons and such.
     
  10. Jul 18, 2011 #9
    Hi QuantumPion, If you say heavy nucleus can decay by carbon emission, is that fact predicted, or is just a discovery after it has occurred. Given a mixture of fissile, fertile and other non-fissile non fertile naturally radioactive atoms, can we predict all possible modes of radioactivity?
     
  11. Jul 18, 2011 #10

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    I have no idea whether heavy decay modes were predicted or observed first.

    I'm pretty sure all the normal natural decay modes have been tabulated by now, unless in the future we discover more stable superheavy elements which decay by other modes.
     
  12. Jul 18, 2011 #11

    Astronuc

    User Avatar

    Staff: Mentor

    I believe that the superheavy elements decay by spontaneous fission or alpha decay.

    http://www.ornl.gov/sci/nsed/outreach/presentation/2011/Roberto.pptx [Broken] (17.3 Mb, use 'save target as')

    International team discovers element 117
    http://www.ornl.gov/ornlhome/news_items/news_100407.shtml [Broken]

    Other information on the production of superheavy elements can be found at www.webelements.com (click on each superheavy element)

    http://www.webelements.com/nexus/chemistry/discovery-elements-atomic-number-114-and-116 [Broken]

    http://www.gsi.de/forschung/kp/kp2/ship/index.html [Broken]
     
    Last edited by a moderator: May 5, 2017
  13. Jul 29, 2011 #12
    All have tried to summarize all existing modes of radioactivity but the core of my doubt : is there any theory to explain the modes observed?
     
  14. Jul 29, 2011 #13

    Drakkith

    User Avatar

    Staff: Mentor

    Quantum mechanics? I'm not really sure what you are asking.
     
  15. Jul 30, 2011 #14
    Quantum Mechanics/Particle Physics, some reactions and modes aren't allowed (conservation of parity, charge, mass etc). The other modes that are allowed have respective transition (decay rates) with certain process being favoured and being faster that others.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Why are there only limited modes of radioactivity?
  1. Radioactive materials (Replies: 1)

  2. Absorbed radioactivity (Replies: 1)

Loading...