Talk:Gyromagnetic ratio

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How atoms/particles change the ratio? is it possible? - Unsigned

Please see WP:RD to get an answer to you question =) --mboverload@ 00:22, 14 May 2006 (UTC)
The following discussion is an archived debate of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the debate was PAGE MOVED - if it's good enough for the IUPAC, it's good enough for me.

Requested move[edit]

Gyromagnetic_ratioMagnetogyric_ratio – The name "magnetogyric ratio" is that which is recommended by IUPAC - the official worldwide Chemistry body responsible for nomenclature, etc. See: Wikipedia should be consistent with current usage.

This is primarily because the value is a ratio of magnetic (i.e. spin) / orbital angular momentum and not orbital / magnetic. Ctrwikipedia 09:55, 8 September 2006 (UTC)


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The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

"Gyromagnetic" vs "Magnetogyric"[edit]

I received a note on my talk page from User:Gillen inquiring about the page move I completed above. Gillen's note:

We need to talk about this gyromagnetic ratio thing. I have never personally heard of the magnetogyric ratio until I had the unpleasant experience of looking at the Lande g factor page today. To say the least, this is disturbing. Please give me more justification for the change than simply some international chemistry reference. Physicists refer to this as gyromagnetic ratio, it appears that chemists think it is the magnetogyric ratio. I can list dozens of physics references that call this the gyromagnetic ratio....please explain to me why they are all wrong?

I'm replying here. I don't have any stake in where this page is; I completed the move because it seemed like a reasonable and cited request, and nobody had opposed after more than a week. Now someone has opposed, so I guess we should talk about it. It would be good to cite an authoritative reference citing each name, if two are in use. The article should be titled according to the most common usage, and the naming discrepancy should be discussed in the article.

All that said, I'm neither a chemist nor a physicist. The Google test gives "gyromagnetic" the edge by 301,000 to 42,100 I would tell the person who requested the move about this discussion, but the account doesn't seem to be active. I'll leave a note at Talk:IUPAC for opinions. Is there a corresponding body that standardizes physics terminology? -GTBacchus(talk) 09:56, 12 November 2006 (UTC)

In physics there is no question as to which word is the correct terminology, since the other one is unheard of (in my experience anyway). I suggest changing all instances of "magnetogyric" to "gyromagnetic" on this page. A note can be inserted saying "(also known as 'magnetogyric' in chemistry)". Rotiro 00:23, 4 July 2007 (UTC)

  • In fact, since the current page name is "Gyromagnetic ratio" and the article acknowledges that this usage is more common, I will be bold and change all instances of "magnetogyric" to "gyromagnetic". Rotiro 00:26, 4 July 2007 (UTC)
I think that's unobjectionable and long overdue. Steve 04:24, 4 July 2007 (UTC)

I disagree with the above rationale which cites IUPAC, since the gyromagnetic ratio is more a physics thing than a chemistry thing. Rotiro 00:37, 4 July 2007 (UTC)

As a chemist, we've used 'magnetogyric' but i agree gyromagnetic is more sensible, if for no other reason than the symbol used in relevant equations is gamma - as in, 'g for gyromagnetic' and not a mu as in 'm for magnetogyric'. — Preceding unsigned comment added by (talk) 17:26, 23 January 2013 (UTC)

As a physical chemistry researcher and lecturer for decades, I have been using "gyromagnetic ratio" simply because, represented by the Greek character gamma in NMR, it is a ratio of nuclear resonance frequency ("the gyro-frequency") to the magnetic field strength ("the magnetic strength"), but not the magnet strength to the gyric frequency. For example, the gamma for 1H nuclei is 42.5759 MHz/Tesla, which means that 1H nuclei will spin at 42.5759 MHz in a magnetic field of one Tesla. Strictly speaking, it is neither a magnetic ratio nor a gyric ratio. Perhaps it can be explicitly called the spin/magnet ratio, the frequency/magnet ratio, or the gyro/magnet ratio. A similar naming example is for the signal to noise ratio, which is widely denotes as the s/n ratio. -- Commented by Wilford Lie on 08/08/2019.

"physics references."[edit]

I couldnt find a body that standardizes physics nomenclature, but I did send you some references. And posted them on your talk page. —Preceding unsigned comment added by Gillen (talkcontribs) 22:22, November 15, 2006 (UTC)

Copied from my talk page:
There are literally thousands of papers that clearly and unambiguously indicate that Lande g-factor/g factor/ gyromagnetic ratio are all synonyms for the same thing. I am including a reference from an old paper that will clearly indicate this.
Rev. Mod. Phys. 34, 102–109 (1962) [Issue 1 – January 1962 ]
It is also clearly illustrated in Griffiths "Quantum Mechanics", as well as in Claude Cohen-Tannoudji's "Quantum Mechanics". FYI - Tannoudji is a Nobel Laureate and Griffiths is the most used undergraduate text that I know of. User:
I've copied the reference information here so it can be worked into the article. I would say the first task is to include in the article discussion of the fact that two names are in common use by different sciences, and if it seems appropriate, we can always move the page back at some point, if it turns out that we find one spelling to be much more common than the other, preferably based on something surer than the "google test". -GTBacchus(talk) 19:53, 20 November 2006 (UTC)

Inconsistency with Larmor frequency page: "also known as Lange G-factor"?[edit]

This page indicates that the magnetogyric ratio is also known as the Lange G-factor. However, there are important factors that distinguish the two. On the Larmor frequency page, they are defined as proportional, with some important dimensionful factors. I'm inclined to believe the equation on the Larmor frequency page, as the equation makes sense unitwise. —Preceding unsigned comment added by (talkcontribs) 19:00, November 20, 2006 (UTC)

Furthermore, I believe it's inaccurate to say the magnietogyric ratio is a "unitless quantity" that gives the ratio between the two moments. When used in the context of the Larmor frequency and energy of nuclear spin excitations, it clearly has dimensions of Teslas/second. —Preceding unsigned comment added by (talkcontribs) 19:02, November 20, 2006 (UTC)

These were fixed when I rewrote the page some time ago. Steve 04:24, 4 July 2007 (UTC)

The sign of the gyromagnetic ratio[edit]

How about the sign the gyromagnetic ratio?

I would like to add that the gyromagnetic ratio (or magnetogyric ratio) of the free electron is - 1.7608... * 10^11 s^-1 * T^-1 and that the gyromagnetic ratio (or magnetogyric ratio) of the proton is 2.6752... * 10^8 s^-1 * T^-1. The opposite signs is convenient when using:

\mu_e = \gamma_e M_s h/(2\pi)

which explains why the magnetic moment of the electron is antiparallell to its spin angular momentum. Agree?

Hakgu (talk) 16:20, 12 December 2008 (UTC)

This page says the electron gyromagnetic ratio is positive. Do other sources say otherwise? --Steve (talk) 18:25, 12 December 2008 (UTC)

A negative electron gyromagnetic ratio can be found for instance in: page 578 in the book "Electron Paramagnetic Resonance" by Weil and Bolton (Weily 2007)

and on page 207 (equation 9) in "Molecular Quantum Mechanics" by Atkins and Friedman (Oxford 2000):

γe = - e/(2*me)

indicating a negative sign.

For the moment I could not find a more available reference... (talk) 12:12, 15 December 2008 (UTC)

OK, that's good. It should be negative to be consistent with the formula and with the nuclear values. I guess NIST figured the sign went without saying...? Anyway, I agree we should change it. --Steve (talk) 19:01, 15 December 2008 (UTC)
Done. Look OK? --Steve (talk) 19:23, 15 December 2008 (UTC)

Gyromagnetic ratio[edit]

The article says the experimetal value of ge, that it is in excellent agreement with the theoretical value...but doesn´t say which one is it. Also, the radian is not a SI unit.-- (talk) 17:09, 30 July 2009 (UTC)

Experimental...I'll make that clearer. The radian is considered a "derived unit" within SI, see radian. It would be good to have a reference for the units of g though... --Steve (talk) 23:13, 30 July 2009 (UTC)

Mathias 29 June, 2011: Regarding the unit: It looks like the "rad" is not really apart of the unit or what? If you simply calculated the ratio (electron change)/(electron mass), then you get the value (up to fine structure corrections) stated in the end of the section "Gyromagnetic ratio for an isolated electron". So what is the "rad" unit doing there?? — Preceding unsigned comment added by (talk) 16:58, 29 June 2011 (UTC)

Axis of symmetry[edit]

The text reads: "Consider a charged body rotating around an axis of symmetry". But just one body rotating around any axix except its own is not rotating about an axis of symmetry. It would be if there were two identical bodies rotating about an axis that goes through the point halfway the two bodies. But with just one body, it does not sound very logical, because you obviously are not referring to the body rotating around its OWN axis. Therefore, I propose to change the sentence into: "Consider a charged body rotating around a point outside that body".Jordaan12 (talk) 17:05, 3 May 2010 (UTC)

The text is referring to the body's own axis. How about: "Consider a charged body with an axis of symmetry, spinning around that axis"? Is that clearer? Any other suggestion? --Steve (talk) 21:02, 3 May 2010 (UTC)

Serious Misconception[edit]

The article says that the correct gyromagnetic factor from "relativistic QM" is 2 + QFT Correactions, while in "classical physics" one would expect this factor to be equal to 1. This is absolutely false. The factor 2 can be obtained from the linearization of both, the classical Schrodinger equation and the relativistic Klein-Gordon equation. Both lead to a 4-spinor, and both linearizations predict the correct gyromagnetic factor to be equal to 2; So the factor 2 is actually a consequence of the dependence of the wave equation on the first (and not the second) derivative with respect to time. So relativity has nothing to do with it. —Preceding unsigned comment added by Fernando.Martin.Maroto (talkcontribs) 17:24, 7 December 2010 (UTC)

Do you have published references for that? If you do, feel free to edit the article yourself. Krashlandon (talk) 17:32, 7 December 2010 (UTC)

Yes. See for example the QM textbook from Walter Greiner. He has a detailed workout of the linearized Schrodinger equation. —Preceding unsigned comment added by Fernando.Martin.Maroto (talkcontribs) 17:48, 7 December 2010 (UTC)

Confusion/error in bottom figure[edit]

I note that the bottom figure, illustrating the two directions of precession, has a confusion or error. Namely, the arrows that are precessing are the spin vectors, not magnetic moment. Yet those arrows are labeled with north and south poles. The magnetic moment itself precesses the same direction, irrespective of the sign of gamma - its just the magnetic moment. It is the spin that precesses either way, depending on the sign of gamma. Bdushaw (talk) 12:06, 3 February 2015 (UTC)

How so? The spin and magnetic moment vectors are either oriented in the same direction or oppositely, depending on the sign of the gyromagnetic ratio, and precess together (i.e. in the same direction around the magnetic field) for any given nucleus. The direction of precessing is determined by whether the sign of gamma, because it determines the sign of the torque on the gyroscopic spin. The precessions in the diagram are correctly opposite. —Quondum 01:55, 4 February 2015 (UTC)
Ah! I see my mistake. The magnetic moments of both sides are the same, but the spins have different signs. Nevermind, except the caption may be clearer in this regard. I would say it differently in this case - the torques on the magnetic moments from the magnetic field are the same in both cases of gamma (the mu's are oriented the same direction, torque is mu-cross-B), but the spins are in opposite directions, so they precess in opposite directions. ("Learning is like simulated annealing. Sometimes we get in local minima of understanding.") Bdushaw (talk) 02:13, 4 February 2015 (UTC)
I've tried to modify the caption to correct how I got confused... Many references, e.g. Shankar Q.M., describe pressesion using the angular momentum vector, rather than magnetic moment. One must pay attention... Bdushaw (talk) 02:20, 4 February 2015 (UTC)
Off-topic, but the following thought occurred to me: are there any nuclei with zero spin, but with a nonzero magnetic moment? For example, deuterium in an excited state (neutron and proton spins antiparallel) might have zero spin, but the unmatched magnetic moments would not cancel. —Quondum 03:02, 4 February 2015 (UTC)
I don't know - does Helium-4 have a small magnetic moment? I find nothing about that by google search. Bdushaw (talk) 03:23, 4 February 2015 (UTC)
I expect it to be exactly zero (due to symmetry: two antiparallel protons, two antiparallel neutrons), though new physics might change this. Candidates would be odd-odd nuclei, but as the link indicates, no stable or short-lived isotopes of this type have zero spin. —Quondum 04:15, 4 February 2015 (UTC)

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