Talk:G-factor (physics)

positive or negative

So, is g_e 2 or -2? As far as I can tell, and as far as I've always read and been taught (and everywhere else on Wikipedia), it's positive, but the NIST [1] link at the bottom definitely says negative. Thoughts? Chris 17:15, 27 May 2007 (UTC)

Well μ=-ρ*g*S/(2*m) so it looks like they included the minus from that. From the other sources no-one seems to bother... Zebas (talk) 11:10, 25 January 2010 (UTC)

The reason the positive/negative value doesn't matter is because of the arbitrariness of the symbols in your equation. You'd usually assign the sign by intuition. Using $\mu =g\mu _{B}m_{s}$, where $\mu _{b}={\frac {e\hbar }{2m}}$ and $m_{s}$ is the value of the spin in the z direction, if you take e as being the negative electron charge, or if you take the absolute value of e there, you can make up for the sign difference in g. The only thing you really need to ensure is that the magnetic moment is in the opposite direction of the electron's magnetic moment. So the minus sign somewhere ensures the vector points the opposite direction. The signs on each element might be different according to conventions, but as long as the whole thing points the right direction, you're fine. 109.255.2.148 (talk) 20:56, 12 May 2011 (UTC)

g factors for elemental particles

Can we calculate (some) of them, or are these just constants to be measured at this point? I think the article could be clearer on this. (Personally don't know the answer.)88.159.72.240 (talk) 12:18, 15 October 2009 (UTC)

There is a constant number for angular and orbital g-factors for electrons and nucleons, at least. There is a formula for the Landé g-factor for electrons (and there's a page for it) and there's a similar formula for the effective g-factor of a nucleus (which is the g-factor shown on the page). 109.255.2.148 (talk) 00:48, 9 May 2011 (UTC)

Renaming and disambiguation

There's now an article named g factor (psychometrics). I want to move this article to g-factor (physical constant), and create a disambiguation page for g factor containing links to both articles. Any comments?--Victor Chmara (talk) 07:54, 28 October 2010 (UTC)

I much prefer g-factor (physics). Other than that, it's fine. :-) --Steve (talk) 16:51, 28 October 2010 (UTC)

OK, g-factor (physics) it is then.--Victor Chmara (talk) 22:23, 28 October 2010 (UTC)

The g-factor is not a universal constant, so it would be wrong to label it so. The spin and orbital g-factors are constants, but with different values depending on if you're using them with electrons/nucleons etc, but the Landé g-factor can change from case to case within electrons/nucleons in an atom depending on the spin, orbital and total angular momentum contributions. 109.255.2.148 (talk) 00:42, 9 May 2011 (UTC)

List

That list is looking a bit weedy.. Is it worth having that there in its own section? Charles Baynham (talk) 15:42, 13 March 2014 (UTC)

dimentionless my foot!!

I would like you to be aware that the calculation for the nuclear magneton is:

e/(2m)ħ=µ_N

the units of µ_N is J/T

and the calculation for gyromagnetic ratio is:

e/(2m)g=γ

the units of γ is radians/second/T (which is converted to MHZ/T by division by 2pi and 10^6)

As is seen here, the difference is the reduced plank, which is in J·Seconds. So the G-factor must be in Radians (because /second and planck's ·Second cancel out) . I feel there is no dimentionless figures, but few want to spend the time to name them! Edit: radians are said to be "dimentionless", being a unit of two dimentional rotation, but I still got to name the unit quantity. Charlieb000 (talk) 21:08, 24 April 2014 (UTC)

Is this anomaly standard?

The electron, muon and proton apparently all have their own masses used in calculating their g-factor, and my perception is that the g-factor would be pretty nonsensical if the particle's own mass was not used. This no doubt holds true for other particles of widely varying masses, e.g. the tauon and various hadrons. However, the neutron seems to be treated here as an exception, in that the proton's mass appears to be used in the calculation of its g-factor. Is this standard, or just a misconception in the way the article is written? The lead uses the phrase "the appropriate fundamental quantum unit of magnetism", which appears to be an oxymoron. It is no more a fundamental unit than the mass of any particle is a fundamental unit of mass for the measurement of all particle masses, and "appropriate" is an ill-defined concept. Could someone with some familiarity in the area comment? —Quondum 16:29, 8 May 2015 (UTC)

I suggest the article needs a general reorganization to fix a few logical problems like this. g-factors for Dirac particles (the leptons, quarks, etc.) are defined differently than g-factors for nucleons, nuclides, and baryons in general (which are defined relative to the nuclear magneton, it seems. The lepton g-factors are close to 2 because their magnetic moments are defined rigorously as an elementary Dirac particle. Baryon g-factors are not so rigorous, since they are not elementary particles. Particles such as hyperons seem to also have g-factors, defined the same way as the neutron's g-factor, viz relative to nuclear magneton. I'd suggest discussing the leptons together in one part of the article, then the composite particles separately. It doesn't help that many articles define the g-factor according to their own local purposes. See the article Neutron magnetic moment where we ran into this question. Bdushaw (talk) 19:08, 10 May 2015 (UTC)

I guess my initial reaction was contrary to the established or traditional approach, which seems to be as you describe it. I have partially reorganized the article to reflect this distinction. Any comments and revisions welcome. —Quondum 20:45, 10 May 2015 (UTC)

I think the autumn 2023 results are missing for the muon

See <https://www.nytimes.com/2023/08/10/science/physics-muons-g2-fermilab.html> Philippschaumann (talk) 09:17, 13 August 2023 (UTC)

Recent measurements

I deleted some entries in the measurement table that are not CODATA and were not referenced. These newer values can wait for the next round of CODATA to be included.

What we really need is a intro paragraph describing how these values are measured. Johnjbarton (talk) 19:18, 19 February 2024 (UTC)