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We know that in a beta minus decay the neutron decays into a proton, electron and electron antineutrino. So let's assume we have a vacuum chamber full of free neutrons which after sometime decay in to its decay products.

So when the neutron gets decayed into a proton does the proton capture the electron which was emitted during the decay process? What will happen to all the electrons in that chamber which were emitted during the decay?

Thanks!

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  • $\begingroup$ Are you asking about a magic inert chamber, or a real vacuum chamber? $\endgroup$
    – Jon Custer
    Commented Jun 12, 2017 at 14:43
  • $\begingroup$ @JonCuster vacuum chamber $\endgroup$
    – Bhavesh
    Commented Jun 13, 2017 at 5:44

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The answer by annav is correct that the neutron decay products will travel in straight paths in a vacuum chamber; the electron and proton will interact with the walls of the chamber, slow down, and become ordinary matter. (Most actual neutron traps involve strong magnetic fields, which make the charged particles travel on non-straight paths, but that seems like a minor detail.)

However: because the neutron decay involves three objects, the distribution of energy and momentum among the electron, proton, and neutrino is random. The total energy released in the decay is roughly 750,000 eV, which is typically shared more-or-less equally between the electron and the neutrino. However, if the neutrino carries away so much of the energy that the electron and proton together have less that 13 eV, the binding energy of the hydrogen atom, then it is possible for the electron to be immediately captured. This is called "bound beta decay", $\rm n \to H+\bar\nu_e$. As of 2014 this process has not been observed.

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The neutron decay products will travel in straight paths if in a vacuum chamber, they will hit the walls and disappear. In any case, neutrons cannot be contained in vacuum. Complicated methods are used in trapping them.

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  • $\begingroup$ Will the proton also disappear? $\endgroup$
    – Bhavesh
    Commented Jun 13, 2017 at 10:15
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    $\begingroup$ The proton will penetrate a bit the wall , grab an electron and become a hydrogen atom. The original electron of the decay will keep the walls neutral $\endgroup$
    – anna v
    Commented Jun 13, 2017 at 10:28
  • $\begingroup$ if we make the walls postively charged such that it generates a positive electric field? Will it still penetrate? $\endgroup$
    – Bhavesh
    Commented Jun 13, 2017 at 10:29
  • $\begingroup$ It will depend on the energy of the proton. The probability of penetrating the first surface is large. In general you can trap the electron and positron in a magnetic field. The problem is upi cannot trap a source of neutrons in a vacuum chamber so as to wait for their decays. $\endgroup$
    – anna v
    Commented Jun 13, 2017 at 18:41
  • $\begingroup$ Re, "Neutrons can not be contained in vacuum." I suppose you mean that neutrons do not interact with the walls of a typical vacuum chamber. $\endgroup$
    – Solomon Slow
    Commented Jun 15, 2017 at 18:11

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