Talk:Larmor precession

Sign

The equation for the Larmor frequency is $\omega {}=-\gamma {}B_{0}$. This means that the sign given in the equation on the page is incorrect. See for example reference 1. --144.32.196.109 (talk) 07:30, 2 September 2009 (UTC)

This is not correct, or at the very least extremely deceptive. It is well known that Hydrogen has a positive gyromagnetic ratio and a clockwise precession, which would be directly contradictory to an $\omega {}=-\gamma {}B_{0}$ equation. This article is likely confusing due to the repetitive reference to a negatively charged particle. In addition there are a numerous references in the literature and established reputable sources that contradict this, for example: page 25 of NMR for Physical and Biological Scientists (Pochapsky & Pochapsky); or Chemistry LibreTexts. The sign should be positive $\omega =\gamma B$, counter-clockwise precession is due to a negative gyromagnetic ratio (which frequently occurs with negatively charged particles). — Preceding unsigned comment added by 150.212.127.24 (talk) 15:52, 25 February 2019 (UTC)

Symbols

Other than B it almost seems like the author went out of his way to use non-standard symbols. In the literature most use tau for torque, rather than capital gamma, and L (sometimes I) for angular momentum, rather than J. It may seem trivial but it confuses and requires the reader to carefully translate in their head each symbol.

FID

Is not Larmor precession exactly the same as free induction decay (FID), in which case should not the articles be integrated, with redirection? GilesW 10:16, 22 September 2007 (UTC)

Just wanted to note that this was answered at the FID talk page. --Qrystal (talk) 22:33, 23 November 2007 (UTC)

Total Angular Momentum?

Was just trying to determine whether this page is referring to the total angular momentum, or just the spin angular momentum. It isn't clear from the context of the page, unless of course, the meaning of J is what makes it clear. If so, wouldn't it be better to be explicit about what J represents, by clearly stating that it means the total L + S? --Qrystal (talk) 22:47, 23 November 2007 (UTC) In practice, this is a very complicated question. Depending on the frequencies used, this can be the frequency of a single object, or a composite object. I think the formula applies generally to any object for which you know the gyromagnetic ratio... although I can't promise. —Preceding unsigned comment added by 75.153.112.114 (talk) 02:22, 2 October 2008 (UTC)

Energy change

what is the energy formula? clearly energy should be released. Since the precession will cause the electromagnetic wave, i.e. the release of photon. it must be in a higher energy state, then precesses and release energy by release a photon to lower energy state. What are two energy levels? and they difference? Jackzhp (talk) 23:05, 17 September 2013 (UTC)

Precession direction

What is the direction of precession? use the cross product helicity? Jackzhp (talk) 22:30, 14 October 2013 (UTC)

The direction of the precession is shown in this video: http://www.youtube.com/watch?v=MOrk9ZQy1Dw. It would appear that the schematic at the top right of this Wikipedia article shows the precession to be in the wrong direction! Or am I missing something? 128.97.129.123 (talk) 02:52, 20 November 2013 (UTC)

I suspect you are right. From HERE, "ω = -dφ/dt (the rotation is left-handed in the direction of B)" The answer may be that the precession of magnetic moment is this way, whereas for a negatively charged particle the spin and magnetic moment are in opposite directions. The small arrow in the figure seems to be the spin angular momentum vector, and the particle is negatively charged. Not sure I am happy with the figure this way. Bdushaw (talk) 11:20, 27 January 2015 (UTC)

The sign of the gyromagnetic ratio, γ, determines the sense of precession. Nuclei such as ¹H and ¹³C are said to have clockwise precession whereas ¹⁵N has counterclockwise precession.

See, for example, this figure from gyromagnetic ratio. For a negatively charged particle gamma is negative. The figure seems to show the spin vectors in both cases, rather than the magnetic moment. Still not happy with that. Bdushaw (talk) 11:35, 27 January 2015 (UTC)

Is the schematic in the top right still wrong? It doesn't look like anyone changed anything. I'm going to change the caption from "the spin angular momentum" to "the magnetic moment", which should fix things because the magnetic moment and angular momentum point in opposite directions for a negatively charged particle... right? Csmallw (talk) 16:08, 28 April 2020 (UTC)

Error in "Including Thomas precession"

The units of angular frequency are wrong in the given formula! — Preceding unsigned comment added by 194.249.198.102 (talk) 11:07, 28 August 2015 (UTC)

This equation has no reference. Its Thomas term does not come from the Thomas precession article. It is suspect because of its finite value in the relativistic limit. If it only pertains to an externally applied field, then it should be so stated.Aqm2241 (talk) 23:32, 9 May 2017 (UTC)

This formula seems wrong to me. The Thomas precession article says that the rotation caused by the double boost from the acceleration electron to the proton's inertial frame is not adding but subtracting frequency to the Larmor term. The Larmor term would be (eB/mc) instead of (eB/2mc) because of the spin g-factor, however, that is the precession rate that would be seen in the electron's local frame but in the proton's frame, the Thomas rotation caused by the electron orbital movement counters half of the rotation leaving it as eB/2mc. — Preceding unsigned comment added by UrielSeptim (talk • contribs) 10:32, 26 December 2023 (UTC)

Bargmann-Michel-Telegdi equation

The BMT equation is a topic of its own. I intend to move it to a separate article. It can easily be cited - Jackson, Gourgoulhon, and Barut quickly spring to mind and there is surely no shortage of papers on it. M∧Ŝc²ħεИ_τlk 21:09, 29 December 2016 (UTC)

This section seems inconsistent in the usage of symbols with respect to the previous one (the factor 2 in front of the magnetic moment $\mu$ appears to be wrong for the usual definition of magnetic moment as given above, and moreover the second version of the equation introduces a capital S which is just what was small a previously. Thasaidon (talk) 21:40, 13 February 2022 (UTC)

In the BMT equation $ds$ is introduced and it is not explained what it is. Perhaps proper time was meant $d\tau$? ChDutsov (talk) 14:28, 10 March 2022 (UTC)