How can beta decay have energy of 3-4 MeV

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Discussion Overview

The discussion revolves around the energy of electrons emitted during beta decay, specifically questioning how electrons can have energies of 3-4 MeV when applying the Heisenberg's uncertainty principle suggests much higher energies for electrons confined in the nucleus. Participants explore the implications of quantum mechanics on this phenomenon.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that according to the Heisenberg's uncertainty principle, an electron confined in the nucleus should have an energy around 3.8X10^8 eV, yet beta decay electrons are observed to have energies of only 3-4 MeV.
  • Another participant questions the assumption that the electron is localized to the nucleus during beta decay, pointing out that it is detected outside the nucleus.
  • A different viewpoint argues that if the electron originates from the decay of a down quark, it must be in the nucleus for a brief period, raising the question of whether it loses energy as it exits the nucleus.
  • One participant asserts that the initial view of decay is too classical and that the electron does not necessarily retain high energy just by being in the vicinity of the nucleus.
  • Another participant emphasizes that electrons can be in the region of the nucleus without their energy increasing significantly, challenging the initial assumption.
  • Further clarification is provided that localizing an electron to the nucleus would indeed increase its energy, but this localization does not occur in the context of beta decay.

Areas of Agreement / Disagreement

Participants express differing views on the localization of electrons during beta decay and its implications for energy. There is no consensus on how the Heisenberg's uncertainty principle applies to the situation, and the discussion remains unresolved.

Contextual Notes

Participants reference quantum mechanics concepts and the behavior of electrons in atomic structures, but there are limitations in the assumptions made about electron localization and energy implications during beta decay.

Moazin Khatri
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First of all let me tell that I am a high school student and I have no background in particle physics.
If we apply the Heisenberg's uncertainty principle to an electron confined in the nucleus it tells us that the energy of the electron must be something like 3.8X10^8eV .. but in a beta decay the energy of the electron is 3-4 MeV.
The moment a neutron decays into a proton and an electron and a neutrino particle the electron will be in the region of nucleus for some small time at least. While in that region, according to Heisenberg's principle it must have such a large energy. But experimentally we find that beta particles have an energy of 3-4 MeV. Why?
Please clarify me as much as possible and correct me wherever i am wrong.
I read about this from this link: http://elearning.vtu.ac.in/e-con/Phys/html/0018.htm
 
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Why do you think the electron is localized to the nucleus in beta decay? Isn't it outside the nucleus when you detect it?
 
If it comes from the decay of a down quark it has to come from the nucleus. And for some small time it will be in that region. And yes that's true that we detect it when it is outside the nucleus but still, the question remains, does it loose energy as it comes out of the nucleus because for some time it would be in the region of nucleus and must have high energy.
 
No, it will not. Your view of how the decay occurs is too classical.
 
Yes sir. I understand that. But if any simpler basic level explanation can be provided I will be very grateful.
I do understand some of the basic ideas of quantum mechanics. So if a simple explanation based on few basic ideas of quantum mechanics can be given I will welcome it.
 
Last edited:
Moazin Khatri said:
some time it would be in the region of nucleus and must have high energy.

That's simply not true. Just being "in the region" doesn't do anything. Forget radioactive decay for a second and just consider atoms. Electrons are sometimes in the region of the nucleus, but there energy doesn't skyrocket when this happens.
 
Vanadium 50 said:
Forget radioactive decay for a second and just consider atoms. Electrons are sometimes in the region of the nucleus, but there energy doesn't skyrocket when this happens.
This depends on what you mean by "sometimes in the region of the nucleus". If you would actually locate the electron to the nucleus this would add a large amount of energy to the electron. It is not the same thing as the wave function having a non-zero value within the nucleus, which is a large part of the reason we have electron capture in some elements.
 
Orodruin said:
If you would actually locate the electron to the nucleus this would add a large amount of energy to the electron.

That's true, but it doesn't happen in either case.
 

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