Talk:Spin isomers of hydrogen

message: Needs explanation as to why the release of heat is undesirable. -- Leonard G. 03:55, 19 Sep 2004 (UTC)
replies: text: I added some content about this aspect a while ago. DMacks (talk) 11:35, 10 February 2018 (UTC)

text: Yes, your reason is correct. To expand a little, the two electrons interact strongly in a bonding molecular orbital, so promoting one to a higher orbital requires a large energy and does not happen at reasonable temperatures. This is in contrast to the nuclear spins which interact very weakly with each other, so that the energy difference between spins parallel and spins opposed is very small and both states are found at normal temperatures. Dirac66 (talk) 23:53, 9 February 2018 (UTC)
thread_title: Needs explanation

message: Why is orthohydrogen refered to as the triplet state, and parahydrogen is the singlet state?
If this page is correct (i.e. ortho- and para- hydrogen refer to alignment of the spins of the two protons in a H2 molecule, not alignment of electron and proton spins in a H atom), then there's a problem with http://en.wikipedia.org/wiki/SHGb02_14a . The problem is that in that article they are referring to alignment of electron and proton spins. I am assuming this article is correct, and removing the reference from the SHGb02_14a article to ortho- and para-hydrogen.
21:22, 30 March 2006 (UTC)
thread_title: Triplet singlet states

message: Move to a more general and descriptive name like nuclear spin modifications of hydrogen or spin isomers of hydrogen? Femto 13:25, 10 August 2006 (UTC)
thread_title:  Rename? 

message: Since virtually all the ambiguitiies mentioned in earlier questions have been addressed and the theoretical basis of ortho- and parahydrogen is now clear, I ve changed this article to Start class.  I don't think I've seen the name "spin isomers" appled anywhere else, so we should consider a different title to this article - I admit that an alternative doesn't occur to me at the moment. Gadolinist (talk) 20:51, 25 November 2009 (UTC)
thread_title: New title?

message: The figures in this article need improvement.
The ortho vs. para figure would be better with a white background, while the graphs on this page are overcompressed in jpeg format. SVG would be better!
129.128.157.245 (talk) 21:38, 9 December 2009 (UTC)
thread_title:  Image cleanup 

message: The article claims that at 20K the ratio of para-H2 in thermal equilibrium
is 99.95%. I've added a "citation needed" for that number.
If I do the math with the partition functions given later in
the article (using EJ = B*J*(J+1) with B=7.35meV) I arrive at
Zpara=1.0000 and Zortho=0.0018, so the given ratio should be ~99.82%.
I've cross-checked my T-dependent curves for Zortho/Zpara with Fig.1
from ApJ 516 (1999) 371, and they perfectly match, so I'm pretty sure
my math is correct.  —Preceding unsigned comment added by 129.206.21.102 (talk) 15:58, 5 March 2010 (UTC)
replies: text: I inserted a reference to Rock's text which has a table showing No/Np = 0.002 at 20 K, corresponding to 99.8% para which value I inserted. And then I noticed your comment, and I see that you and Rock are in agreement. Dirac66 (talk) 02:02, 6 March 2010 (UTC)
thread_title:  para/ortho ratio at 20K 

message: Although this section is factually correct, it is poorly written and cited. First off, the reference for PASADENA is not the actual paper where the term is first published. There is also no mention of the related ALTADENA effect.  Second the oxford-instruments page is no longer valid.  3rd, the Duckett group site from York and one of their papers are referenced but oddly there is no mention the the SABRE phenomenon in the article. I think this section needs to be rewritten and expanded.  The PHIP review article by C.R. Bowers would be an excellent source to add.  — Preceding unsigned comment added by Danny31292 (talk • contribs) 22:01, 27 May 2014 (UTC)
thread_title:  NMR section 

message: There is a relevance tag for the statement that the 3-fold degeneracy of orthohydrogen can be broken by a magnetic field. I think that the 3-fold degeneracy is important because it is responsible for the 3:1 population ratio. However if we just call it a degeneracy without referring to a magnetic field, some readers will say yes, but the levels are not degenerate in a magnetic field. So we need to say in the absence of a magnetic field in order to be completely correct. I think that phrasing is a bit more to the point than can be broken by a magnetic field.
As for the other relevance tag two lines further down, the non-degeneracy of parahydrogen is also necessary to explain the population ratios. The only flaw I see with that sentence is that it repeats the point 3 times in slightly different words, but in a general encyclopedia this may be necessary for some readers. I am going to remove these 2 relevance tags. Dirac66 (talk) 02:31, 30 June 2016 (UTC)
thread_title:  Relevance tags for magnetic field and non-degeneracy