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[Beta decay] Nuclear physics

  1. Aug 23, 2014 #1

    smk

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    What is difference between beta particle and electron? I mean in spin, mass or other properties.
     
  2. jcsd
  3. Aug 23, 2014 #2

    Simon Bridge

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    Nothing.
     
  4. Aug 23, 2014 #3

    smk

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    Thanks
     
  5. Aug 23, 2014 #4

    Simon Bridge

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    No worries - conceptually a beta particle comes from a nuclear disintegration, so it is a handy shorthand.
    Saying I detected a beta particle from some atom is a bit different from saying I detected an electron from that atom.

    Given a free electron, there is no way of telling if it came from a nucleus or an electron shell or pair production even.
    You need some other information - like the presence of a beta-unstable radio-isotope, and shielding.

    Historically, beta rays were named before they were identified with cathode rays and so with electrons.
    Technically beta particles may be positive or negative - but we would usually specify "beta-plus" if the positron is intended.

    It's all good fun.
     
  6. Aug 24, 2014 #5

    smk

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    Thanks alot
     
  7. Aug 24, 2014 #6

    smk

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    Thanks I m confused when I studied that in beta decay W- decay into electron and antineutrino. when we see the spin of w- then it is -1.this is TRUE only when electron and antineutrino both have spin half (down).sir this is my own thinking may be I m wrong.thanks
     
  8. Aug 24, 2014 #7

    Nugatory

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    Beta decay is a process by which a beta particle - which is an electron - is produced along with an antineutrino as a proton converts into a neutron. Yes, this terminology is somewhat confusing.... It came about for historical reasons, because the radiation was observed and given its name before the particles involved were identified and the process understood.
     
  9. Aug 24, 2014 #8

    smk

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    Thanks
     
  10. Aug 24, 2014 #9

    Simon Bridge

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    ##p^+ \to n^0 + e^- + \bar \nu_e## does not conserve charge?

    You mean: ##n^0 \to p^+ + e^- + \bar \nu_e##

    To conserve angular momentum, the electron and neutrino spins need to be aligned - you are thinking.

    The usual sin-up/spin-down terminaology only applies in an external magnetic field like that of the nucleus of an atom on in a Stern Gerlach apparatus. There is no "up" or "down" in space.

    Odd things can happen in the virtal particle transition though - consider, is total energy conserved as the W -> e+nu. ?
     
  11. Aug 24, 2014 #10

    smk

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    Sir you mean that here we cannot consider spin?sir what do you think energy is conserved here.since we know that W is havier .and if we try to re combine electron and antineutrino then what happen?
     
  12. Aug 24, 2014 #11

    Nugatory

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    D'oh... Yes, of course.
     
  13. Aug 24, 2014 #12

    jtbell

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    The W in this case is "virtual". Energy and momentum are conserved, but the mass of a virtual particle is generally not the same as the mass of a "real" particle. Particle physicists often use the jargon "off the mass shell" for virtual particles, where "on the mass shell" means "having the mass that you see in the standard tables."
     
  14. Aug 24, 2014 #13

    smk

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    Thanks jtbell
     
  15. Aug 25, 2014 #14

    Simon Bridge

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    I think smk wants a definitive answer to the conservation of angular momentum issue ;)
    If electron and neutrino spins must be aligned, then that suggests the proton must have the opposite of the spin of the initial neutron.
     
  16. Aug 25, 2014 #15

    smk

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    Thanks
     
  17. Aug 25, 2014 #16

    smk

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    And another question arise here that as we know that in nuclei protons and neutrons occupy definite levels in nucleonic shells.now question is that when neutron transformed into proton then where the proton goes? I mean it will stay in the same level as that of neutron or jump into another level? Thanks
     
  18. Aug 25, 2014 #17

    ChrisVer

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    In strict language, yes there would be a small jump(due to coulomb potential). The nucleus itself can change.. but in general and simple models this doesn't happen, because the strong force doesn't distinguish between neutrons and protons (isospin symmetry).
     
  19. Aug 25, 2014 #18

    smk

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    Thanks
     
  20. Aug 25, 2014 #19

    mfb

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    To be small, you need very special nuclei like Tritium.
    In general, neutron and proton numbers in a nuclei are so different that the most high-energetic occupied neutron state and the available unoccupied proton states have different quantum numbers.
     
  21. Aug 25, 2014 #20

    ChrisVer

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    hmm... Do for example the higher atomic number mirror nuclei differ much from each other?
     
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