Sodium emission spectrum

  • #26
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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.
 
  • #27
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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?
 
  • #28
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I'm not sure I know what a red led indictor lamp is...
 
  • #29
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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.
 
  • #30
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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.
 
  • #31
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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
 

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  • #32
Vanadium 50
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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"?
 

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