Talk:Electron paramagnetic resonance

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Article's title[edit]

I moved this talk page, and the article's contents, to Electron Paramagnetic Resonance because essentially everything on the page referred to EPR, not ESR. - Astrochemist 19:10, 25 May 2007 (UTC)[reply]

Surely EPR and ESR are just different terms for exactly the same thing? 130.88.80.227 (talk) 13:06, 9 January 2012 (UTC)[reply]

Needs for the article[edit]

Relaxation times
Saturation effects
Effect of multiple unpaired electrons on an atom/in a molecule - tukan 17:19, 13 Dec 2004 (UTC) and Dirk Beetstra ^{T C} 15:15, 21 July 2006 (UTC)[reply]
Spin traps - Jasoninkid
Instrumentation? - Astrochemist 15:37, 24 May 2007 (UTC)[reply]
The applications section is weak for such a long article. - Astrochemist 15:37, 24 May 2007 (UTC)[reply]
Something on field modulation describing how first derivative measurement is made. - EvilxFish (talk) 17:24, 18 April 2017 (UTC)[reply]
The instrumental part describing how ESR spectrometers are constructed is quite weak if not absent.150.227.15.253 (talk) 11:51, 3 May 2017 (UTC)[reply]
The instrumental part needs illustrations! 150.227.15.253 (talk) 13:25, 12 October 2022 (UTC)[reply]

Content and organization[edit]

Equation cannot be read in the text. Please modify the format so that it appears correctly. —Preceding unsigned comment added by 220.227.97.99 (talk) 14:11, 22 January 2010 (UTC)[reply]

I moved some of the introductory material to sections further down in the article. This allows the reader to see the contents box more easily. - Astrochemist 03:37, 10 May 2007 (UTC)[reply]

I removed the following:

"Beyond these considerations, as

\nu

increases the n_{M_J+1} grows exponentially, so high-field EPR spectra are saturated at lower P as compared with X-band measurements."

I deleted the above sentence as I could not readily see how raising a spectrometer's frequency would cause the upper energy state to be more populated. It seems that just the opposite would be true. Am I missing something? - Astrochemist 04:43, 22 May 2007 (UTC)[reply]

Do we need an animated gif in the final section? How about a simple picture showing several spectra, each at a different microwave frequency? - Astrochemist 02:24, 23 May 2007 (UTC)[reply]

I don't think so. In fact, a good deal of this article has been written by somebody with a particular interest in high field ESR, hence all the links to Russian stuff. I would suggest that the final section could be spun out to a new article on high field ESR, since the article is already getting on the long side. Good work on this article though - I've been meaning to do it for ages and never got round to it! Chris 08:08, 23 May 2007 (UTC)[reply]

PS: Do we really need to give g to all those decimal places? It's given on the g-factor page, though it has a different value there!.

I agree with what you wrote above. I changed the picture with the nitroxide spectra (now a bit fuzzy) and I see that you've altered g_e. -- Yesterday I traced the high-field EPR material to a Russian lab's web pages, and added the appropriate link. Since those pages have a copyright notice, I'm not sure how much of their material can be used in this particular Wikipedia article. -- Astrochemist 15:37, 24 May 2007 (UTC)[reply]

Something basic here, "The parallel alignment corresponds to the lower energy state, and the separation between it and the upper state is

\Delta

E = g_eμ_BB₀, where g_e is the electron's so-called g-factor (see also the Landé g-factor). " Maybe μ_B should also be defined? —Preceding unsigned comment added by 92.48.72.35 (talk) 18:33, 16 October 2008 (UTC)[reply]

Yikes! That should have been done long ago. I just now made the addition. - Astrochemist (talk) 20:22, 16 October 2008 (UTC)[reply]

Theory Section[edit]

Maxwell-Boltzmann Distribution[edit]

The article supplies an equation for sensitivity and refers to the "minimum number of detectable spins" but doesn't specify the conditions. I believe this is the minimum detectable spins for a signal-to-noise ratio of 1? Furthermore, no definition or reference is provided for the constant k1. A reference would be very helpful here. One possible reference is Rinard et. al. Chompx (talk) 23:22, 18 May 2010 (UTC)[reply]

It would also be nice to add a section describing line broadening and the relevance of the Bloch equations. Chompx (talk) 23:22, 18 May 2010 (UTC)[reply]

The g-value section[edit]

NMR spectroscopists usually interpret changes in line positions in terms of shielding constants ( $\sigma$ ), but EPR spectroscopists usually interpret changes in line positions in terms of g-value variations caused by spin-orbit coupling. This Wikipedia article has both, so I'd like to remove the shielding constant material. (It can always be put back in if I'm wrong.) -- Astrochemist 19:21, 24 May 2007 (UTC)[reply]

Errors in the article[edit]

The magnetic moment of an electron is approximately the Bohr magneton, it is NOT the gyromagnetic ratio of the electron times the Bohr magneton (which would approximately be the Larmor frequency). Changes in the resonance frequency of an electron in a chemical environment do not arise from changes in either the spin angular momentum or the gyromagnetic ratio. The former is a fundamental property of any spin 1/2 particle, while the latter is a fundamental property of the electron. Rather, the coupling of the electron magnetic moment to nuclear magnetic dipoles, or the spin-orbit coupling alters the energy difference between the spin up and spin down states, leading to a frequency change the provides information about the chemical environment. In simpler terms, the local magnetic field an electron experiences depends on it environment, so different chemicals cause slighty different field strengths at the electron, and thus shifted resonance curves (and different linewidths!).

The initial version of the above was added anonymously on 21:41, 6 April 2006 192.55.208.10. I believe that the points raised have been corrected. - Astrochemist 19:21, 24 May 2007 (UTC)[reply]

EPR questions[edit]

How is elecron spin resonance used to date material?

I read the following on the BBC news website, concerning the dating of the human footprints in the Americas (article Footprints of 'first Americans' by Paul Rincon - link http://news.bbc.co.uk/1/hi/sci/tech/4650307.stm).

The researchers used radiocarbon dating on shells and animal bones in the sequences and dated mammoth teeth by a technique called electron spin resonance. The sediments themselves were dated by optically stimulated luminescence.

Answer: Radiocarbon dating uses, that the composition of Isotopes depends from the age. Usually one uses a mass-spectrometer to measure the composition. I guess, that ESR is used, because its not invasive, so the Object will not be harmed/destroyed by the measurement. The annormal Zeeman-effect leads to different line-structures in ESR-measurement, if you have different Isotopes. From the Absorption-Intensities one can conclude the composition and indirectly the age? I know that this is theoretically possible, but I doubt whether it is an accurate method.

Can ESR be used as a technique for analysis of antioxidants???

Answer: Yes kinda, ESR can see free radicals, especially with the use of a spin trap, therefor ESR can see free radicals going away and thus the affect of the antioxidants. - Jasoninkid

Technical Diagram describing instrument technique[edit]

I think it would be extremely beneficial to add a graphic to describe the technique. One example that I have seen is on YouTube here. Any help would be appreciated! --MarsInSVG (talk) 16:46, 4 October 2011 (UTC)[reply]

Section "Miniature electron spin resonance spectroscopy with Micro-ESR"[edit]

The section labelled "Miniature electron spin resonance spectroscopy with Micro-ESR" seems to not fit properly, as several things that are listed under this headline do not belong to "micro-ESR" but rather to the previous section "Applications". I suggest removing the unreferenced text from "Miniature electron spin resonance spectroscopy with Micro-ESR" up to "Applications include real-time monitoring of free radical containing asphaltenes in (crude) oils, biomedical R&D to measure oxidative stress, evaluation of the shelf life of food products." After this removal, the remainder should fit consistently into "Applications".HBook (talk) 16:49, 9 December 2016 (UTC)[reply]

I now separated the sentences mentioned above into a separate section to make the "applications" section coherent again. I also removed a very "marketing-like" sentence about disadvantages of conventional ESR compared to "micro-ESR", which to me was not convincing (and was unreferenced). Actually, the whole "micro-ESR" section is still unreferenced, and therefore I would still consider it reasonable to remove this section completely: I think that the mentioned development of Caltech are not unique, but that there are several groups working in this direction.HBook (talk) 11:45, 14 February 2017 (UTC)[reply]

Review request[edit]

Please could someone review the section on the hardware involved in making the EPR measurement (Hardware components) and check the accuracy of the information presented. EvilxFish (talk) 15:20, 3 July 2017 (UTC)[reply]

Minuturization[edit]

The following section was removed: " Miniature electron spin resonance spectroscopy with Micro-ESR: Miniaturisation of military radar technologies allowed the development of miniature microwave electronics as spin-offs by the California Institute of Technology and Rice University. Since 2007 these sensors have been employed in miniaturized electron spin resonance spectrometers called Micro-ESR. Applications include real-time monitoring of free radical containing asphaltenes in (crude) oils, biomedical R&D to measure oxidative stress, evaluation of the shelf life of food products.<ref>Yang X., Chen C., Seifi P., Babakhani A., Integrated electron spin resonance spectrometer, US Patent 9689954</ref>" --Smokefoot (talk) 15:49, 1 January 2018 (UTC)[reply]