Difference between parallel and antiparallel spins?

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Discussion Overview

The discussion centers on the differences between parallel and antiparallel spins for nucleons, exploring concepts related to nuclear pairing, the Pauli Exclusion Principle, and the implications of spin orientation on binding energy. The scope includes theoretical aspects of nuclear physics and the behavior of nucleons under the influence of the nuclear force.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that nucleons tend to pair with either parallel spins (both spin up or both spin down) or antiparallel spins (one spin up and one spin down), questioning the implications of the Pauli Exclusion Principle on this pairing.
  • Another participant asserts that two nucleons cannot pair with the same spin state, although they can occupy different spatial states with the same spin orientation.
  • A participant notes that nucleons have a tendency to pair due to the nuclear force, indicating that parallel spins correspond to both nucleons spinning in the same direction, while antiparallel spins involve one nucleon spinning up and the other down.
  • There is a question raised about whether there is an energy difference between nucleons with parallel versus antiparallel spins.
  • Another participant poses a question regarding why nucleons with parallel spins are more strongly bound to each other compared to those with antiparallel spins.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Pauli Exclusion Principle and the nature of nucleon pairing, indicating that multiple competing views remain regarding the binding energy and spin states of nucleons.

Contextual Notes

There are unresolved aspects regarding the energy differences between parallel and antiparallel spins, as well as the specific conditions under which nucleons can pair with the same spin state.

says
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What is the difference between parallel and antiparallel spins for a pair of nucleons?

My understanding is that nucleons have a strong tendency to pair - proton with proton, neutron with neutron, proton with neutron. When they pair their spins either:

cancel (spins pair antiparallel) pairing of a spin-up and spin-down nucleon
add (spins pair parallel) pairing of two nucleons with both spin up or both spin down

Am I understanding this correctly? - I'm thinking I might be missing something in regards to the Pauli Exclusion Principle. How can two nucleons with the same spin state pair?
 
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says said:
How can two nucleons with the same spin state pair?
They cannot.
You can have two nucleons in different (spatial) states with the same spin orientation, however.
 
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So nucleons have a strong tendency to pair due to the nuclear force, which has a spin component. When nucleons pair their spins will either be:
(Parallel) - Both spin the same way
(antiparallel) - One nucleon spin up and one spin down

Is there an energy difference between the two as well?
 
A more important question - Why are nucleons with parallel spin more strongly bound to each other than those having anti-parallel spin.
 

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