Can an orbital have both electrons and positrons?

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Discussion Overview

The discussion centers on the possibility of a stable atomic structure that includes both electrons and positrons in atomic orbitals, particularly in the context of phenomena such as beta-plus decay. Participants explore theoretical scenarios, potential interactions, and the implications of such configurations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether a stable nucleus could contain both electrons and positrons, suggesting that positrons could occupy outer shells depending on the nuclear charge and electron distribution.
  • Another participant proposes that the attractive potential from remaining negative charge after beta-plus decay might allow for a positron to remain in orbit.
  • Concerns are raised about the high kinetic energy of positrons in beta-plus decay, which may exceed the binding energy of any potential orbit.
  • One participant speculates that a temporary bond could form between a negative ion and a positron, although this is challenged by the likelihood of annihilation.
  • Another participant asserts that annihilation is a significant outcome when electrons and positrons interact, referencing the concept of positronium as a counterexample to stable configurations.
  • A later reply discusses the definition of "stable," suggesting that an exotic atom could be considered stable if neutral and long-lived, but argues against the feasibility of such a state due to wavefunction overlap leading to rapid annihilation.

Areas of Agreement / Disagreement

Participants express differing views on the stability of configurations involving electrons and positrons, with no consensus reached on whether such systems can exist in a stable state. The discussion reflects a range of hypotheses and concerns regarding annihilation and binding energies.

Contextual Notes

Participants highlight the importance of definitions, such as what constitutes stability, and the implications of wavefunction overlap in determining the likelihood of annihilation. The discussion also touches on the limitations of current understanding regarding exotic atomic structures.

TheCanadian
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Can there be a stable nucleus where one has both electrons and antielectrons (either paired or unpaired) in the atomic orbitals? For example, in a ##\beta ^+## decay, could the antielectron released by captured by the atom and remain in orbit as an electron may?
 
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Think ! For an orbit the least you need is an attractive potential !
 
BvU said:
Think ! For an orbit the least you need is an attractive potential !

Yes, could not the anti electron occupy an outer shell (which is unoccupied), and thus depending on the number of protons in the nuclei versus closer electrons in the orbitals (which is attractive), these could be competing forces. I am wondering if such a scenario has been observed or if other plausible scenarios exist.
 
Ah, I get the idea. The remains after a ##\beta^+## is negative and that would provide an attractive potential ?
However, as a rule, the remains eject an electron to return to neutral.

In ##\beta^+## decay the kinetic energy of the e+ is a lot higher than the binding energy from a diffuse and unstable cloud with net charge 1e-
 
But if a negative ion and a positron came together, I guess it should be possible for them to form a bond, at least temporarily.
 
No. They annihilate. See first sheet here
 
They only have some probability of annihilating. If you can have things like positronium or even crazier things like di-positronium, I see no reason why you couldn't have this, albeit for a short time.
 
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I'm no QED expert but I suppose you can calculate probabilities. But annihilation should score 'rather' high...
@vela @Orodruin : Was my first answer overhasty ?
 
This hinges on the definition of "stable". I would say that this exotic atom is stable if a) it is neutral, and b) its lifetime in its ground state is long - say one second. Using that definition, the answer is "no".

The simplest system that satisfies a) is a positron orbiting an H- ion. An H- ion has a radius almost the same size (just a tiny bit larger than) as an H atom, and the radius of an atom formed by a positron orbiting a -1 charge object is the same as an H atom. So essentially the two electrons and the positrons will be in the same orbitals, and will therefore have substantial wavefunction overlap. That means they will annihilate quickly - on positronium-like time scales: nanoseconds.

This argument extends to Z+1 electrons and one positron orbiting a nucleus of charge Z: if you're in the ground state, the positron's S-wave wavefunction overlaps substantially with all the electrons in an S-wave.
 
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