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Intersize Particle Interaction

  1. Sep 15, 2009 #1
    Can an electron travelling near the speed of light knock a proton or neutron out of a nucleus?
  2. jcsd
  3. Sep 15, 2009 #2
    Yes, it can.
  4. Sep 15, 2009 #3
    Thanks Bob. I see that you are a theoretical physicist. I am having trouble finding any info on this. Do you know the proper web search parameters to get this info or of any specific info that is available on the web so that I can study this? Thanks.
  5. Sep 15, 2009 #4
    I am not good at this kind of phenomena. It may be called element transmutation, nucleus excitation/splitting, deep inelastic scattering, or so. Sorry.
  6. Sep 15, 2009 #5
    Hi gonegahgah-
    Most of the electron-nuclear reactions go via a single-photon coupling, so experimenters use electrons to produce a bremsstrahlung beam and measure photo-nuclear reactions. Most reaction channels are gamma-neutron, with thresholds being around 20 MeV for low-Z and 6 to 8 MeV for high-Z targets. Some targets, like aluminum-27 go via other channels, like 2p n, to sodium 24. At high Z, cross sections are over 1 barn; for low Z maybe 10 to 20 millibarns. Bremsstrahlung in air produces a lot of nitrogen-13 and oxygen-15, both short half lives.
    Bob S
  7. Sep 16, 2009 #6
    Thanks Bob & Bob.
    I looked up those terms you suggested Bob4.
    Nuclear transmutation seems to involved a lot more energy than a single electron on its own can offer.
    Nucleus excitation seems to be more about capture of ions and electrons rather than knocking out protons.
    Nucleus splitting seems to involve sending in neutrons; not electrons.
    The deep inelastic scattering did involved firing electrons into the nucleus but these don't seem to have dislodged the protons or neutrons; only the electrons themselves emerged.
    I might be wrong on those of course so please correct me.
    At the moment I'm not sure which of these might apply or if something else might apply.
  8. Sep 16, 2009 #7
    Hi gonegahgah-
    Nuclear transmutation is done primarily by neutron capture. neutrons are produced primarily by neutron capture and proton bombardment, and less efficiently by electron bombardment (via single photon exchange).
    Atomic (not nuclear) excitation is more about ion and electron capture.
    Nuclear splitting (fission) is done primarily by neutrons.
    Electron elastic scattering was used to measure nuclear sizes. Electron deep inelastic scattering led to discopvery of partons, now called quarks.
    Bob S
  9. Sep 16, 2009 #8
    Thanks BobS.
    It is also the photons I am curious about as well.
    I'm trying to get a feel for the intersize particle 'heftiness'.
    Electrons have about 1/1836 the mass of of a proton (1/1839 of a neutron).
    This makes it harder for electrons to push protons around I imagine than vice-versa; the electrons go where the proton goes; not vice-versa.
    When hydrogen fuses to helium the conversion of mass to energy is about 1/142 the mass (a site said 0.7%; that is 1/142 isn't it?).
    More mass than that contained in an electron is converted is it? Wow!
    But that doesn't correspond to a single photon does it?
    Afterall normal light scattering due to 'electron excitation and photon re-emission' doesn't correspond anywhere near that relative quantity of energy.
  10. Sep 17, 2009 #9
    The electron and bremsstrahlung photon energies that we are talking about here for nuclear transmutation are in the MeV region, so this energy corresponds to binding energies of nucleons. The deuteron binding (dissociation) energy is about 2.2 MeV, for example. The normal light scattering and "electron excitation and photon re-emission" you mention is an atomic, not nuclear, excitation process.
  11. Sep 19, 2009 #10
    Thanks BobS. I'm okay with that. I was just mainly wondering about the energy released through fusion. All that large amount of energy released from a single instance of fusion isn't released as a single photon is it? That would be one big photon if it was?
  12. Sep 19, 2009 #11
    Fusion reactions usually yield strong-interaction products (neutrons, etc) rather than electromagnetic (photons). For example, the D-D fusion yields a tritium or helium-3 plus a neutron (2.5 to 3 MeV), and the D-T fusion yields an alpha particle plus a 14.1 Mev neutron.
    Bob S
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