Register to reply 
Nuclear Spin 
Share this thread: 
#1
Sep114, 02:24 PM

P: 246

Is there a theoretical basis for the spin of the nucleus of an arbitrary atom? I'm looking at this website: http://hyperphysics.phyastr.gsu.edu...ear/nspin.html



#2
Sep114, 02:42 PM

Mentor
P: 12,113

The value is the sum from the individual nucleons: their angular momentum and their spin.
Both protons and neutrons have energy levels similar to the electrons, but their energy structure is more complicated. Pairs always cancel out, but you can have a single proton or neutron (or both) leading to the total spin. If you know the structure of the energy levels, you can predict the state they are in, and therefore the total spin. 


#3
Sep114, 05:04 PM

Emeritus
Sci Advisor
PF Gold
P: 16,471

I agree with what you say except for "pairs always cancel out". To pick a nucleus at random, Vanadium50 is spin 6+. Lots of aligned pairs.



#4
Sep114, 05:08 PM

Mentor
P: 12,113

Nuclear Spin
Vanadium 50 is odd/odd, you have two unpaired nucleons there. That is the "or both" case I mentioned.



#5
Sep114, 05:30 PM

Emeritus
Sci Advisor
PF Gold
P: 16,471

That gets you to spin1. It's 6+.
Pierce, to get back to your question, the answer is "yes", but it's not simple. The short answer is that you have shells like you do in atoms, but because of the fact that the nuclear interaction is more complicated than electromagnetism, the order in which the shells fill moves around quite a bit, and you can end up with bizarre situations like 12 of 50 nuclei all spinning in the same direction. 


#6
Sep114, 05:38 PM

P: 246

Is this kind of stuff studied in QCD?



#7
Sep114, 05:48 PM

Mentor
P: 12,113

@pierce15: QCD is more relevant "inside" hadrons. Nuclear physics uses effective models as a full QCD analysis gets too complex for large nuclei. 


#8
Sep114, 07:10 PM

Emeritus
Sci Advisor
PF Gold
P: 16,471

As mfb said, it's too hard to study a system like V50 in QCD. It has 150 valence quarks.



#9
Sep114, 07:23 PM

P: 246

So do are all the protons and neutrons (or individual quarks) in a nucleus described by orbitals?



#10
Sep114, 07:49 PM

Emeritus
Sci Advisor
PF Gold
P: 16,471

Yes, the nuclei are in orbitals, but predicting these orbitals is harder than it is in chemistry.



#11
Sep114, 07:53 PM

P: 246

Does the Schrodinger equation then describe the system? If so, what would the potential be for ionized deuterium?



#12
Sep114, 07:56 PM

P: 1,066

It's not "hard" to study QCD for nuclear physics... I'd better say it's meaningless... QCD stops working perturbatively at the nucleus range [energies]. So your results are not predicting at all...
Yes the Schrod. equation can describe the system [because the nucleons are not relativistic]. You can look for the potential... it depends on what interactions you allow... eg some standard potential well for the nuclear force, maybe spinorbit coupling, spinspin coupling etc... The nuclear potentials in general can be very difficult to be determined, they can contain many terms, some coming from "theoretical" background, others coming straightforward from experiments, and then other experiments are needed to determine your parameters. 


Register to reply 
Related Discussions  
Nuclear spin  High Energy, Nuclear, Particle Physics  0  
Nuclear spin  High Energy, Nuclear, Particle Physics  5  
Nuclear spin confusing  Advanced Physics Homework  5  
Nuclear Spin  Advanced Physics Homework  1  
Nuclear spin and parity  Advanced Physics Homework  0 