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Sodium emission spectrum

  1. May 11, 2009 #1
    I was doing an undergrad experiment on the sodium emission spectrum and I have a few queries. Of course, I was asked to analyse the famous yellow doublet which I'm on top of. I was also asked the analyse the diffuse series which was fine too.

    What I did notice however, was a strong red line that wasn't in the diffuse series. I was told to do somme research about its origin but I've had absolutely no success in finding any information online or in books yet. It seems that most information online just focuses on the bright yellow doublet.

    This wavelength wasn't even measured and I can hardly be expected to go through every possible energy difference and try to find the one that's the best match. There must be an easier explaination.

    We were also given, for the practical task, a list of transition levels. That got me wondering - why are there so many omissions? I was again told to do some research, specifically on why there aren't transitions between the s and d series. I was thinking of something along the line of not conserving spin etc but I can't quite put my finger on it.

    Thank-you for your help.

    In summary, you could say my questions are:

    -Where the hell does the strong red line in the sodium emission spectrum come from?
    -Why the hell are the sodium electrons so stubborn that there won't be any transitions between s and d series.

    Thank-you kindly in advance.
     
  2. jcsd
  3. May 11, 2009 #2

    alxm

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    Try this http://physics.nist.gov/PhysRefData/ASD/lines_form.html" [Broken]

    There are two important selection rules governing electronic transitions. You mentioned spin: That's one. It's the other one.
     
    Last edited by a moderator: May 4, 2017
  4. May 11, 2009 #3
    Thanks for the help mate.

    I used the database. I did a search between 6200 Angstrom and 6500 Angstrom, the smallest wavelengths in the red section. I got stacks of answers though. I have no idea what to pick. In the diagram that I have, it simply has 1 red wavelength labelled that I was asked to research, as if it's particularly special.

    As for the other part, okay. Not spin but... angular momentum?
     
  5. May 11, 2009 #4
    Still a bit lost when it comes to these questions. Any more help would be much appreciated. Do you have any more help alxm perhaps?
     
  6. May 11, 2009 #5

    Vanadium 50

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    How sure are you this is from sodium?
     
  7. May 11, 2009 #6
  8. May 11, 2009 #7

    Vanadium 50

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    And none of the strongest lines there are red.

    Let me ask my question again: How sure are you this is from sodium?
     
  9. May 11, 2009 #8
    It was in a dark room with only a slight bit of ambient light. Could it possibly be from that?

    Also, any more help on the s - d series transitions?
     
  10. May 11, 2009 #9
    (See my post above on NIST Table) There are four red lines between 6500 and 6700 Angstroms belonging to ionized (missing 1 electron) sodium. There is nothing in un-ionized sodium in this range.
     
  11. May 11, 2009 #10

    Vanadium 50

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    Yes there are. None of these lines are labeled "persistent" and none of them has a particularly high intensity. The OP says he/she is looking for a strong line. Hence my question.
     
  12. May 11, 2009 #11
    I am uncomfortable with the answers Einstein2nd has been getting in this thread. People seem to be suggesting that with a bit of hard work, a clever undergraduate ought to be able to figure out the answers to these questions. If that is in fact what people are intending to suggest, I just want to register my disagreement. I think these are pretty hard questions. If someone knows where the red line comes from, I wish they'd explain it. As for the missing lines, I do have some idea of where the selection rules come from in terms of the hydrogen atom, but I don't find the extension to sodium to be entirely straightforward. It's certainly not the kind of thing I'd ask an undergraduate to try and figure out for himself.
     
  13. May 11, 2009 #12
    With your question about why there are no s-d transitions it is because of the need to conserve total angular momentum. In a transition the difference between the angular momentum of the two states must differ by exactly one unit as the photon will also have one unit of angular momentum.
    Not sure if I have explained it well, if you want to check it you could try looking at Modern Physics by Serway, Moses and Moyer on pages 280-281 (not sure if you have access to this but it is the only place I know off hand that has it)
     
  14. May 12, 2009 #13

    Vanadium 50

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    Well, we do tend not to want to just give answers here. You would see this more had this been in the Homework section. As far as the red line, I keep asking the question that is a Big Fat Hint. If someone were to answer it...
     
  15. May 12, 2009 #14
    In a theoretical sense, I agree that sometimes if you answer a question to quickly, you deprive the questioner of the opportunity of figuring it out for himself. But I also think there are situations where a straight question deserves a straight answer.

    Since I don't know where the red line comes from, I can't positively say that from a pedagogical standpoint this is situation A or situation B. I can make all kinds of guesses: I could imagine that there is a UV emmision from the Sodium spectrum that is down-converted to the optical range by a process in the glass walls of the tube, and that is the source of the red lines. But that would be a blind guess: and if you told me it was right or wrong, it would in neither case contribute to my understanding of quantum mechanics. For my sake, I'd rather just be told the explanation up front.
     
  16. May 12, 2009 #15

    Vanadium 50

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    I agree. But "here's a homework question" is not one of them.

    I also note yet again, that nobody is trying to answer my question. It's a huge hint.
     
  17. May 12, 2009 #16
    But it's not a homework question. It was something the student noticed that was beyond the scope of his undergraduate lab, and when he asked his instructors about it he was told to "go do some research". So he's come here to ask the question.

    You say no one has tried to follow up on your hint. I speculated that it might be something in the glass. If that's not even close enough to count as "trying", then I can't imagine what the right answer is.
     
  18. May 12, 2009 #17

    Vanadium 50

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    Let me say it again. How sure are you this is from sodium? I did not say "guess where it's coming from". Answer the question asked.
     
  19. May 12, 2009 #18
    Yes you did.
     
  20. May 13, 2009 #19

    Vanadium 50

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    Baloney. I challenge you to point out where I used the word "guess". You won't be able to because your statement is utterly, completely and totally false.

    You can whine and moan all you like about being cryptic - the fact of the matter is that this is for a course (and I note in passing that the OP disregarded the sticky to post the question in the appropriate area) so I am not going to give him the answer, instead, I asked a question as a hint. That question has not been answered, so it's a little disingenuous to be complaining that the hint isn't good enough.

    You want to discuss the science, I'm here. You want to make false statements about what I have written, I'm through here.
     
  21. May 13, 2009 #20
    Actually, I didn't enter this discussion so much for the science as to ask why the OP wasn't getting a straight answer to his question. I had the vague impression that people were for some reason playing mind games with him. I'm glad you've cleared this up.
     
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