What is the origin of the strong red line in the sodium emission spectrum?

[Einstein2nd]

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 explanation.

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.

 

[alxm]

-Where the hell does the strong red line in the sodium emission spectrum come from?

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

-Why the hell are the sodium electrons so stubborn that there won't be any transitions between s and d series.

There are two important selection rules governing electronic transitions. You mentioned spin: That's one. It's the other one.

 

[Einstein2nd]

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?

 

[Einstein2nd]

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?

 

[Vanadium 50]

Where the hell does the strong red line in the sodium emission spectrum come from?

How sure are you this is from sodium?

 

[Bob S]

Some of the lines are from neutral sodium (Na I), and some from singly ionized sodium (Na II). Here is a table and database of all sodium lines from NIST:
http://physics.nist.gov/PhysRefData/Handbook/Tables/sodiumtable2.htm

 

[Vanadium 50]

Some of the lines are from neutral sodium (Na I), and some from singly ionized sodium (Na II).

And none of the strongest lines there are red.

Let me ask my question again: How sure are you this is from sodium?

 

[Einstein2nd]

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?

 

[Bob S]

(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.

 

[Vanadium 50]

(See my post above on NIST Table) There are four red lines between 6500 and 6700 Angstroms belonging to ionized (missing 1 electron) sodium.

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.

 

[conway]

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.

 

[Low_Profile]

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)

 

[Vanadium 50]

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.

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...

 

[conway]

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.

 

[Vanadium 50]

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.

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.

 

[conway]

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.

 

[Vanadium 50]

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.

 

[conway]

I did not say "guess where it's coming from".

Yes you did.

 

[Vanadium 50]

Yes you did.

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.

 

[conway]

You want to discuss the science, I'm here. You want to make false statements about what I have written, I'm through here.

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.

 

[psylo]

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 explanation.

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.

-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.

If your experiment manual really omitted a clear instruction to measure the red wavelength, that sucks - but are you sure that's the case?
Secondly, did your manual have a diagram of energy transitions? is that what you mean by a "list of transition levels"? If so, then you could at least estimate which transitions are most likely to be responsible for the red line, by comparing energy levels to those in the diffuse series that you are confident about.

As ALXM suggested (your first response), the NIST database is great - to make it easier if you use it next time, consider the "relative intensity" column. I searched for emissions between 590 (yellow) and 750 (supposed end of red spectrum), and the emission with the highest relative intensity was exactly what you need. Look at "configurations" rather than "terms"...

Can I just ask, why are people so surprised at these questions for undergraduate students? I don't think they are at all unreasonable in this context and answers are readily available (not just online!), even without complete understanding one could sufficiently answer the questions (which isn't that good from a learning perspective).

 

[psylo]

How sure are you this is from sodium?

what einsten2nd may have omitted was that they were given a "sodium spectrum" diagram in which to identify the origin of this red line may also be a big hint for him :P

 

[Dadface]

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.

Let me have a guess.I'ts predominantly red,i'ts intense enough and at a position such that the light can enter the spectrometer.I think Rudolph popped in or could it be something else?From where I am sitting now I see some little red lights which would look fairly intense in a dark room.

 

[OONeo01]

As far as the red line goes, search for impurities in the Sodium Spectrum. Possible Neon impurities.

 

[emuswimguy]

The red line is a sodium D-line emission, that is present in high-pressure sodium lamps. Sodium lamps that have even higher pressures can also contain blue-violet lines that are mainly due to mercury. In most sodium lamps you will only see the yellow doublet but your lamp could very well have these lines.

 

[Brendy]

The red line is a sodium D-line emission, that is present in high-pressure sodium lamps. Sodium lamps that have even higher pressures can also contain blue-violet lines that are mainly due to mercury. In most sodium lamps you will only see the yellow doublet but your lamp could very well have these lines.

I think I'm doing the same experiment as OP and the lab manual states that the sodium D-line is the yellow line which is actually a doublet. I'm not sure what the red line is either as it was too faint to get an accurate measurement.
As for Vanadium 50's hint, it seems that he's implying that the line is caused by impurities in the lamp. That's what I take from the hint anyway.

 

[Dadface]

I think I'm doing the same experiment as OP and the lab manual states that the sodium D-line is the yellow line which is actually a doublet. I'm not sure what the red line is either as it was too faint to get an accurate measurement.
As for Vanadium 50's hint, it seems that he's implying that the line is caused by impurities in the lamp. That's what I take from the hint anyway.

Do you have any red led indicator lamps in your lab?

 

[Brendy]

I'm not sure I know what a red led indictor lamp is...

 

[Dadface]

I'm not sure I know what a red led indictor lamp is...

The little lamps you have on appliances like power packs.I was just wondering if there were other light sources in the lab.

 

[Brendy]

Oh, you mean light emitting diodes? I can't speak for OP but in my lab we had curtains that closed off each bench from the rest of the lab so there was very little light other than that from the sodium lamp. There may have been a little red light on the power switch on the power supply but considering that both OP and I have had the red line come up and then be asked about its origin makes me think that it wasn't caused by another light or something that wasn't meant to happen. I think its probably something to do with the lamp itself like it being high pressure (I'm not sure if mine was high pressure or not) or some impurities in the lamp.

 

[Bob S]

Here is a high pressure sodium spectrum from www.umd.edu[/url] in the first attachment, and a listing of visible sodium lines from [url]www.nist.gov[/URL] in the second attachment. In the sodium spectrum, a triplet of red lines is visible. In the NIST table, a quartet of red lines near 6500 Angstroms from ionized sodium are shown. Three of the red lines in the Table are spaced at about 15 Angstroms, and the fourth is only 1.7 Angstroms away, and is probably not resolved. The three red lines visible in the spectrum are probably the three lines listed in the Table.

Bob S

 

[Vanadium 50]

Bob, that was the wrong explanation a year ago when you first posted it, and it's the wrong explanation now. He's looking for strong lines, and the lines you have posted are weak.

High pressure sodium is irrelevant. He says he's studying the D-lines, and you have pressure broadening in high pressure sodium that makes this impossible - indeed, there you can have emission in the red: the D-lines can get that broad.

Sodium does not have any strong red lines. However, a sodium vapor tube can have all sorts of other things in it. Mercury, argon and neon are all commonly present. Before trying to figure out why an element without strong lines in the red somehow has strong lines in the red, wouldn't it make sense to ask what exactly is in the tube? And indeed, wasn't the reason spectroscopy was developed to answer the question "which elements am I looking at"?