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Neutron proton hit

  1. Mar 15, 2009 #1
    Hi everybody

    When fast neutrons hit isolated protons (eg. hydrogen cores in paraffin) the neutrons kinetic energy is transferred to the proton (as they have aproximatly the same mass), which is detectable by a geiger counter, while the neutron is stoped.

    Thats how far I got after several days of searching the net. But no article tells me what happens to the hydrogens electron, which is now left without a atomic core to relate to.

    I haven't been able to come up with a sensible solution myself, so I'm asking you guys whether you have any idea.

    Thanks for your replies
  2. jcsd
  3. Mar 15, 2009 #2


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    The electron's binding is so small with respect to MeV, that it is just left alone by itself.
    It will drift until it is captured somewhere.
    The neutron is not "stopped" the n and the p recoil as in any elastic collision.
  4. Mar 15, 2009 #3


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    Only if the neutron smacks the proton head on, with the velocity vector aligned the protons cm would the neutron lose maximum energy and be close to stopping. Most of the time, the reaction is one of scattering.

    The proton recoils and it's positive charge will excite and ionize other atoms in the material through which it recoils. Where the proton comes to rest, it would represent a net positive charge, and the electron would represent a net negative charge where it remained. But in between there is a line of mobile and excited electrons, so there will be a cascade of mobile electrons which move to retain charge neutrality. In the process, photon are emitted and it is these photons that enable photodectors to measure levels of radiation.
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