Talk:Rotational–vibrational spectroscopy

nu bar

One of the equations at the bottom has nu instead of nu-bar at one point (should be obvious, cf. other equation) - I don't know how to fix this. The author also seems randomly to believe there is a HCl spectrum on the page, from the last paragraph? Nessa Carson (talk) 15:49, 4 March 2012 (UTC)

I noticed the mention of Cl isotopes and reference to absent image as well. This looks iffy, as if the text has been lifted from another source inappropriately. 150.203.123.59 (talk) 03:26, 20 November 2012 (UTC)

Thank you both. I have replaced spectrum shown above by spectrum of HCl, for example. I also traced the origin of this passage, which was moved in 2006 from the article Rotational spectroscopy. That article had contained a spectrum of HCl, which was removed on 7 Dec 2005 with an edit summary saying that the image file had been deleted (from Wikipedia). This suggests that there had been a copyright problem with the image, rather than the text. It just took 7 years for someone to notice that the text referred to a nonexistent spectrum. Perhaps someone can find (or draw) another spectrum of HCl without a copyright problem? Dirac66 (talk) 12:05, 20 November 2012 (UTC)

Possible new title (or move)

Would this article be better renamed Rotational-Vibrational Spectroscopy, which is the name of the main section and seems to describe the article better? Do others think that the article should be renamed (or moved in Wikispeak)? Dirac66 (talk) 23:25, 10 November 2012 (UTC)

I strongly agree with the suggestion above (re-naming to Rotational-vibrational spectroscopy). Aside from giving a more accurate description of the content of this page, it will also allow for better connectivity with other forms of spectroscopy that are described in Wikipedia.Nnrw (talk) 18:14, 16 November 2012 (UTC)18:14, 16 November 2012 (UTC)

Thanks for your support. I have now gone ahead and re-named the article, and spelled vibrational with a small v as per your comment. And while I was at it, I also renamed the French translation to fr:Spectroscopie rotationnelle-vibrationnelle. Dirac66 (talk) 02:47, 17 November 2012 (UTC)

Major re-write

Please check for typos, errors etc. Can anyone contribute actual spectra, particularly for symmetric tops? Petergans (talk) 09:23, 23 December 2012 (UTC)

We have permission from SpectraCalc to show simulated spectra created on their web-site. I am in the process of clearing this with WP.permissions, so that we can upload simulated spectra. The simulations without line-width are actually easier to understand than real spectra because component lines are "resolved" so that the underlying structure is easier to see. I will put in the parallel band from CH₃Cl 680-780 cm^-1. For perpendicular bands we could use 1300-1400. 1400-1500 or 3000-3100 cm^-1. Unfortunately there is a restriction to 100 cm^-1 range for non-subscribers. Other possibilities are nitric oxide,NO, 1830-1930 (lambda doubling) and nitrous oxide, NNO, 540-640 cm^-1, a nice example of a perpendicular band in a linear molecule. Petergans (talk) 10:51, 4 January 2013 (UTC)

Simulated CO spectrum

Several questions re the simulated CO spectrum:

1. What is the correct source for this redrawn spectrum, please? The footnote says Hollas p.67 which is actually in the chapter on point group symmetry. Hollas p.131 has the HCl spectrum. Perhaps it is p.67 of some other book?

Correct book is Banwell&McCash. I created the diagram in EXCEL using the equation and constants taken from Banwell&McCash, on p70 (ref. 4).

1. Are the two weak lines near 2140 cm^-1 supposed to be a Q-branch? CO is diamagnetic so should not have a Q-branch.
2. Or are they supposed to be the last line of the P-branch and the first line of the R-branch? If so, there should be a gap between them, as in Hollas Fig.6.8 (p.131) for HCl. This zero gap separates the P and R branches so that they can be identified, especially if the lines closest to the gap are not as weak as shown here. Dirac66 (talk) 01:09, 6 January 2013 (UTC)

I found the errors in the spreadsheet and uploaded a new png, but it does not seem to show. Petergans (talk) 10:23, 6 January 2013 (UTC)

OK, thanks. Are references 11 and 12 (stretching and bending modes for HCN, cited as Hollas p.76-78) also supposed to be Banwell and McCash? The stretching band is in Hollas p.156, but not the bending band. Dirac66 (talk) 04:52, 7 January 2013 (UTC) Yes. I've renamed the CO spectrum so it now shows correctly. Petergans (talk) 09:47, 7 January 2013 (UTC)

Two meanings for quantum number K

As is to be expected in an article based on different sources, there is (at least) one notational conflict. In the paragraph on dioxygen, the symbol K is the quantum number for molecular rotation before nuclear spin is added to give J. However in the section on symmetric tops, K is the component of J about the molecular axis. Since both meanings relate to part of the total J, there is a risk of confusion for some readers. Since the symmetric top usage is much more widespread (at least in textbooks), I think the best choice would be to follow Hollas and relabel the dioxygen K as N. If the other sources cited use K (I haven't checked), we can mention in the footnotes that their K is our N. For the moment I added such a mention to the footnote citing Hollas, but that can be removed if we change the symbol in the text. Dirac66 (talk) 23:54, 10 January 2013 (UTC)

Combination differences for Raman - typo in Hollas

In the section Raman spectra of diatomic molecules, the combination difference formulas are now given as

$\Delta _{4}^{\prime \prime }F(J)={\bar {\nu }}[S(J)]-{\bar {\nu }}[O(J)]=4B^{\prime }(2J+1)$

$\Delta _{4}^{\prime }F(J)={\bar {\nu }}[S(J-2)]-{\bar {\nu }}[O(J+2)]=4B^{\prime \prime }(2J+1)$

Yes, these are correctly copied from Hollas p135 except that one typo in Hollas has been fixed by restoring the missing F. However there is a second typo in Hollas which I will fix - $\Delta _{4}^{\prime \prime }$ and $\Delta _{4}^{\prime }$ have been interchanged. This is clear from the line preceding equ. (6.39) in Hollas which states that $\Delta _{4}^{\prime \prime }$ is a function of B" only (not B' as his printed equation implies), and also from the line following equ. (6.40), and finally by analogy to the IR combination differences on Hollas p132. Dirac66 (talk) 16:45, 15 January 2013 (UTC)

Copyright

We now have the needed permission to show diagrams created in Spectracalc. Via e-mail to me personally, received 16 January 2013

Yes, these Creative Commons terms are perfectly fine. Martin McHugh, GATS Inc

Petergans (talk) 13:37, 17 January 2013 (UTC)

Definitions of band, sub-band, subspectrum?

In the section on Symmetric top molecules, what exactly are the definitions of sub-band and sub-spectrum? What sets of transitions constitute a sub-band and a sub-spectrum?

And for that matter, what exact set of transitions constitutes a band? All rotational transitions corresponding to the same vibrational excitation, or only some? This latter question could be answered at the first mention of the word band. Dirac66 (talk) 22:12, 21 January 2013 (UTC)

OK, Hollas p122 defines a band (in the gas phase) as all the lines for a given vibrational transition, which is clear and can be stated in the article. What about sub-band and sub-spectrum? Dirac66 (talk) 01:40, 22 January 2013 (UTC)

I took the names from Allen and Cross. I've changed the names to sub-structure to avoid ambiguity. Petergans (talk) 09:36, 22 January 2013 (UTC)

OK then, what constitutes a sub-structure exactly? It cannot be an arbitrary subset of a band, since we refer to a well-defined centre of a sub-structure. And it must be larger than a branch, since we refer to the Q-branch of a sub-structure. I am seriously wondering if substructure (or sub-band or sub-spectrum) is just a synonym for an entire band which is of course a subset of the whole spectrum. If that is not correct, please explain what the words do mean. Are they used in a more recent book? (I don't have Allen + Cross). Dirac66 (talk) 16:30, 22 January 2013 (UTC)

Or perhaps the meaning (of each term) is variable but well-defined in a specific context (such as Allen + Cross?). In that case the meaning in the context of the Wiki article needs to be better defined. Dirac66 (talk) 17:04, 22 January 2013 (UTC)

I'm no expert here. Hollas, p.158, says virtually nothing about perpendicular bands. On p.100 he gives the formula for pure rotation in a symmetric top, excluding centrifugal distortion, as

$F(J,K)=BJ((J+1)+(A-B)K^{2}$

The selection rule for a perpendicular ro-vib band means that for every value of J there are 2 values of K, so the "sub-structure" is not exactly like a PQR structure. I don't see how to clarify this without going into a great deal of detail, which I feel is not warranted. Quite the opposite, I've removed the sentence about rotational fine structure. Petergans (talk) 12:08, 23 January 2013 (UTC)

We could mention the PQR branches only in the section on parallel bands, such as the spectrum shown for the C-Cl stretch in CH₃Cl.

Also I will specify that each "sub-structure" we are talking about corresponds to a band. In principle the word "sub-structure" refers to an observed set of lines with some pattern, which could be a larger or smaller set of lines, perhaps one P-branch. The ones we are talking about are those which are interpreted as complete single bands. Dirac66 (talk) 02:54, 25 January 2013 (UTC)

Vibronic spectroscopy

I have created that article and propose to submit it for "Did you know?". Any suggestions/revisions will be welcome, before I submit it.

That article concludes the trio of articles in which rotational transitions may be involved. Are there any repercussions on this one and rotational spectroscopy? Petergans (talk) 08:07, 11 March 2013 (UTC)

punctuation, spelling, notation . . . .

Please: WP:MOS and WP:MOSMATH exist.

I found things like

J-1

instead of

J − 1

i.e. a hyphen rather than a minus sign, no proper spacing, and the J was not italicized. (One italicizes variables in this context, but not digits and not parentheses, etc. See WP:MOSMATH. This is consistent with TeX usage (i.e. inside <math> tags) and these things are taken care of automatically when they are within TeX.)

I found lots of instances of things like

pp29-31

instead of

pp 29–31

i.e. no space between "pp" and the numeral, and a hyphen instead of an en-dash. In at least on case there was something like p 29–31, i.e. a single "p" even though it's more than one page.

Michael Hardy (talk) 03:52, 26 May 2013 (UTC)

Yes, the previous editors of this article (including me) have been concentrating on getting the science right and not worrying about the Wikipedia style manuals. Thank you for taking care of this editorial aspect. On my computer keyboard, it is easier to type J-1 or at least J - 1 with a hyphen as a short minus sign, because the "hyphen" only requires typing one character which is easy to find on my computer keyboard, next to the zero. Dirac66 (talk) 16:27, 26 May 2013 (UTC)

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