Do Protons and Neutrons Move around in the Nucleus?

  • #26
Dale
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I agree. Please post the new question to a new thread. The connection to this thread is tenuous at best, as far as I can tell.
 
  • #27
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You can of course do QM calculations that show non-spherical nuclei.

Very nice picture, and more. The dogleg shaped nuclei are a big surprise to me. Are these time independent?
 
  • #28
e.bar.goum
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Very nice picture, and more. The dogleg shaped nuclei are a big surprise to me. Are these time independent?
Ah, no, it's a Time Dependent Hartree Fock calculation of the 40Ca + 238U quasi-fission reaction, shown at two different angular momenta, what you're seeing is different time-steps. For the L=80 case, for instance, you see the 40Ca come in, the two nuclei form a neck between them, they rotate for about a 1/4 turn, then re-seperate, with fairly similar masses to what they started with. The L =20 case is similar, except the sticking time is longer, and the mass-transfer is larger.

Usually, when you see these simulations they're done as a video. I don't have any to hand, but I will see if I can dig one up, they're really neat.
 
  • #29
e.bar.goum
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Ah, no, it's a Time Dependent Hartree Fock calculation of the 40Ca + 238U quasi-fission reaction, shown at two different angular momenta, what you're seeing is different time-steps. For the L=80 case, for instance, you see the 40Ca come in, the two nuclei form a neck between them, they rotate for about a 1/4 turn, then re-seperate, with fairly similar masses to what they started with. The L =20 case is similar, except the sticking time is longer, and the mass-transfer is larger.

Usually, when you see these simulations they're done as a video. I don't have any to hand, but I will see if I can dig one up, they're really neat.

Success! Found some gif's in Wakhle et. al. PRL. 113 (2014). http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.182502
Bonus: It's also 40Ca + 238U. Each frame is 0.3 zs.
L=20

L_20.gif

L=80
L_80.gif


ETA: The L=20 case doesn't seem to auto-loop. Refresh the page if you can't see it move.
 
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  • #30
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Ah, no, it's a Time Dependent Hartree Fock calculation of the 40Ca + 238U quasi-fission reaction, shown at two different angular momenta, what you're seeing is different time-steps.

Of, course, how foolish of me.

Usually, when you see these simulations they're done as a video. I don't have any to hand, but I will see if I can dig one up, they're really neat.

That would be very nice to see.

I did a short search on images of "nuclear orbitals" and came up empty. Do you have anything like this? It would be fairly in line with the OPs initial question.
 
  • #31
e.bar.goum
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Of, course, how foolish of me.



That would be very nice to see.

I did a short search on images of "nuclear orbitals" and came up empty. Do you have anything like this? It would be fairly in line with the OPs initial question.

See above. :wink:

I've never seen a "picture" of nuclear orbitals like the ones you see for atoms (e.g. http://www.sccj.net/publications/JCCJ/v5n3/a81/fig1.gif) although there is a relationship - you have the same angular momentum coupling in nuclei too, but there's ... more - you can't ignore spin-orbit coupling, for starters. The picture that comes to my mind would be the Nilsson model, showing the single particle energy levels for nucleons:
fig1.png


Where ##\beta## is the deformation of the nucleus. Then, you can realise that these are single-particle levels, and you can then build a rotational band on top of each of these. You can then compare that to a set of atomic energy levels.

But this is way more intimidating than is actually educational, unless you're already familiar with this sort of thing. o_O

(ETA - each number there is a number of nucleons. Solid vs dashed lines indicate parity. The colours indicate subshells)
 
  • #32
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See above. :wink:
You're very kind.
I've never seen a "picture" of nuclear orbitals like the ones you see for atoms (e.g. http://www.sccj.net/publications/JCCJ/v5n3/a81/fig1.gif) although there is a relationship - you have the same angular momentum coupling in nuclei too, but there's ... more - you can't ignore spin-orbit coupling, for starters. The picture that comes to my mind would be the Nilsson model, showing the single particle energy levels for nucleons:
fig1.png


Where ##\beta## is the deformation of the nucleus. Then, you can realise that these are single-particle levels, and you can then build a rotational band on top of each of these. You can then compare that to a set of atomic energy levels.

But this is way more intimidating than is actually educational, unless you're already familiar with this sort of thing. o_O

Not at all educated on nuclear physics(!), which is why us, unfamiliar with the discipline, like pictures--at least, I do. In searching "Nilsson model" I did find one apparently relevant pictorial, prepending an advertisement for a class course in what appears to be Liverpool.
 
  • #33
e.bar.goum
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You're very kind.


Not at all educated on nuclear physics(!), which is why us, unfamiliar with the discipline, like pictures--at least, I do. In searching "Nilsson model" I did find one apparently relevant pictorial, prepending an advertisement for a class course in what appears to be Liverpool.

HAH! Your link kicked something in my mind. Naturally, you can get these kind of pictorial representations in TDHF calculations! I have slides showing 16O states! Unfortunately, it's not something I have online. But, here are a selection of examples. These show density.
Screenshot from 2015-07-06 15:29:55.png


Screenshot from 2015-07-06 15:29:55.png
Screenshot from 2015-07-06 15:30:14.png
Screenshot from 2015-07-06 15:30:48.png
Screenshot from 2015-07-06 15:30:54.png
Screenshot from 2015-07-06 15:31:11.png
 
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  • #34
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Nice.

They are very peculiar, and not at all like superpositions of s, p, d, f electron orbitals, with weirdly, less symmetry.

Are they derived theoretically or from experimental data?

Of course, experimental data is interpreted through theory, but what I mean to ask is---I'm not really sure how to put it. Maybe you can enlighten me.
 
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  • #35
e.bar.goum
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Nice.

They are very peculiar, and not at all like superpositions of s, p, d, f electron orbitals, with weirdly, less symmetry.

Are they derived theoretically or from experimental data?

Like I said, they're TDHF calculations for 16O. I don't know that you could get these from experiment - nuclear shapes are the sum of all of these orbitals. However, the input nuclear force for this particular simulation is derived from experimental data. (For the experts, it's Skyrme SLy6). Now, a valid question would be -- "how well does TDHF, being a mean field approximation, reproduce the shapes of orbitals?", to which my answer is, I've no idea. :sorry:
 
  • #36
RaulTheUCSCSlug
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Wait, did some one start a new thread for the different question?
Are you saying it's a different question entirely? Then you should start a new thread.
 
  • #37
e.bar.goum
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Wait, did some one start a new thread for the different question?
I don't think so.
 
  • #39
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It's also worth pointing out that it is predicted that amongst the neutral pions that mediate between the neutrons and protons, there are charged pions that would turn a neutron into a proton and a proton into a neutron (e.g. a neutron (udd) emitting a negative pion (dū) becomes a proton (uud) and the proton absorbing the negative pion becomes a neutron). Some sources predict the protons and neutrons '..are constantly in flux, changing state every 10-23 seconds..'.

Sources-
Pions
Structure of the Nucleon: Pions and Quarks (section 'Three types of pions')
Introductory Nuclear Physics page 94
 
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  • #40
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The interaction can be given under the assumption that the forces are derivable from a potential which depends upon the relative spin orientation of the particles but apparently not upon whether they are protons or neutrons. In order to obtain some insight into the binding of the nucleus, we assume the simplest possible forces and test the consequences of these assumptions by experiment.
 
  • #41
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In any model assumed the energy level gaps have to be millions of times more I think.Any readjustnents among nucleons must invove titanic effects in reference to atom overall.It is evident due to radiations like gamma rays emitted.
 

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