Understanding the Unbound Nature of the nn-Pair in Nuclear Clusters

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Discussion Overview

The discussion centers around the nature of the nn-pair (neutron-neutron pair) in nuclear physics, specifically addressing why it is considered unbound and exploring its potential existence in certain isotopes as a cluster state. The scope includes theoretical considerations and references to nuclear cluster states.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question the meaning of "unbound" in the context of the nn-pair, suggesting that it lacks a force to hold two neutrons together.
  • One participant expresses frustration with the explanation of unbound states, seeking a deeper understanding related to isospin and the comparison to the deuteron.
  • Another participant notes that while the nn-pair is not bound in a free state, it may exist as a nucleon cluster state in isotopes, referencing historical and recent studies that suggest the di-neutron could be a cluster structure in certain isotopes like He-8 and He-6.
  • Links to various studies and literature are provided to support the existence of di-neutron clusters and their implications in nuclear physics.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the nn-pair, with some agreeing on its unbound status while others propose that it may exist in specific cluster states. The discussion remains unresolved regarding the implications of isospin and the comparison to the deuteron.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of nuclear forces and the definitions of bound versus unbound states. The references to various isotopes and cluster states introduce additional complexity that is not fully explored.

malawi_glenn
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Why is the nn-pair unbound? I don't seem to find the answer in any of my textbooks =/
 
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Why is the nn-pair unbound?

What do mean by "unbound"? If you are wondering why there is no such entity as a double neutron, there is nothing to hold two neutrons together.
 
That was a very good answer, not. Do you think I am that noob on physics that I have not figured it out my self? Saying that something is unbound and "there is nothing that can hold it togheter" is pretty much saying the same thing.

Someone who has studied nuclear physics who can help me? mathman seems to be a retired mathematician..

I was thinking that neutron + neutron has isopspin 1 and the deutron (the bound state of neutron + proton) has isospin 0. So does it has something to do with that?
 
Last edited:
To malawi_glenn:

While it is true that N-N pair is not "bound" in free state (as you say due to isospin constraint), this does not mean it does not exist as a nucleon cluster state in isotopes as a type of resonance:

1. The di-neutron (N-N) was suggested as a cluster structure moving around some isotopes as long ago as 1969 by L. Pauling:
http://www.pnas.org/cgi/reprint/64/3/807.pdf

2. Di-neutron cluster structure has recently been suggested in He-8 isotope (see page 8 for explanation of what is means to say N-N cluster may exist):

http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.2120v1.pdf

and here for He-8:
http://www.ujp.bitp.kiev.ua/papers/460302p.pdf[/URL]

3. Also for He-6:
[PLAIN]http://www.maik.ru/abstract/nuclphys/0/nuclphys10_0p1724abs.htm[/URL]

4. Di-neutron cluster predicted in O-18 isotope:

http://prola.aps.org/abstract/PRC/v16/i1/p475_1

5. Di-neutron long ago was predicted to be a by-product of certain fission events:
[url]http://www.nature.com/nature/journal/v165/n4201/abs/165722a0.html[/url]
but I have no idea if the experiments suggested have been conducted.

6. See also "halo nuclei" literature:

http://theory.gsi.de/hirschegg/2003/Proceedings/Al-Khalili_131.227.115.66_alkhalili.pdf
[PLAIN]http://www.ingentaconnect.com/content/maik/10637788/2000/00000063/00000010/00000965[/URL]

Hope these links are of some use to you.
 
Last edited by a moderator:
Thanx, yes they can exists in cluster. But I was referring to the analogy with the deutron only.

Thanx again, will look at the links :D
 

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