Talk:Spin (physics)

"Relation to orbital angular momentum"

As far as I can tell, the current section "Relation to orbital angular momentum" is just "mumbling". Nothing in the section explains any relationship. The Belinfante/Ohanin/Sebens field models make the connect plain: the total angular momentum of the field factors into spin and orbital parts. Johnjbarton (talk) 18:39, 11 February 2024 (UTC)

Spin magnetic moment

I think we should merge Spin magnetic moment into this article. Johnjbarton (talk) 03:47, 15 February 2024 (UTC)

Agreed.--ReyHahn (talk) 10:32, 16 February 2024 (UTC)

 Done Johnjbarton (talk) 18:37, 16 February 2024 (UTC)

Measurements of spin?

I have been trying to find reference describing the experimental verification of spin values. Tough going ;-).

I found

• R Fernow Introduction to experimental particle physics:
  • "The spins of the electron and nucleons have been determined from the hyperfine structure in optical spectroscopy, from atomic and molecular beam experiments, or from experiments in bulk matter using magnetic resonance techniques [6]. The spins of the charged pions have been determined using the principle of detailed balance, which relates the cross section for a reaction with the cross section for the inverse reaction [7]"

However ref 6 "Methods of Experimental Physics volume 5 Nuclear Physics Part B L. C. L. Wu Yuan" is very obscure. Ref 7 is

As far as I understand it, there is no direct way to measure spin (I've seen that in some ref but can't find it now).

Let me know if you have any hints. Johnjbarton (talk) 00:31, 20 February 2024 (UTC)

Try the Stern-Gerlach effect. Xxanthippe (talk) 02:01, 20 February 2024 (UTC).

Sure, I assume that is what my ref means by "atomic beam". That's fine for the z component of spin of a charged particle but it does not tell us about the total spin and it does not work on uncharged elementary particles. Johnjbarton (talk) 02:50, 20 February 2024 (UTC)

What about the Zeeman effect? --ReyHahn (talk) 09:19, 20 February 2024 (UTC)

This might be one step removed from the detection of spin, but Einstein–de Haas effect does indicate that magnetization (and eventually spin) is a form of angular momentum. Jähmefyysikko (talk) 14:48, 20 February 2024 (UTC)

Thanks for all of these suggestions! I guess I should have been more specific. There are a lot of sources for electron spin and I want to include all of the ones suggested. However, I was looking for information on any of the other Standard Model particles. I found a ref only for pions. I'll keep digging. Johnjbarton (talk) 17:11, 20 February 2024 (UTC)

If you are looking for the magnetic moment of the proton see Immanuel Estermann.--ReyHahn (talk) 10:59, 21 February 2024 (UTC)

I did find a good review article by Estermann which I used for the nuclear spin paragraph.

I have been learning a lot! The subject of this article is "spin", rotational angular momentum, which is a quantized magnitude per particle (eg 1/2 or 1). The projection of spin on an externally set (magnetic) axis is also quantized (eg +/- hbar/2), an it is variable depending on the energy state of the particle. The magnetic moment is not quantized but is proportional to the projection of spin on the axis. Thus these three are related but independent physical quantities. Johnjbarton (talk) 16:20, 21 February 2024 (UTC)

Error spin animation !

In the part on Direction, section Vector the 3D example seems wrong : the green 'belt' is rigid, not twisting on itself like the blue and the red do : Defective representation. The following looks more like it : Appropriate representation. Notice that the vertical (blue here) is actually twisting ! Zigomar7 (talk) 04:55, 29 March 2024 (UTC)