Sodium Vapor Lamps (low pressure) for spectral calibration and diffraction work

In summary, a high-pressure sodium lamp can be used as a quasi-coherent VIS, double peak source without a lot of clutter on either side of the peaks.
  • #1
fsonnichsen
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Just curious if anyone out there is using the old low pressure sodium vapor lamps for spectral calibration and diffraction work. I was surprised that I do not see any bench ready laboratory lamps from the usual vendors. I understand that the last manufacturer of the low pressure bulbs, Philips, has discontinued them.
They were quite handy for testing spectrometers splitting the two Na peaks at about 0.6nm.

Does anyone know a reasonable substitute for a quasi-coherent VIS, double peak source without a lot of clutter on either side of the peaks?
thanks
fritz
 
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  • #2
Define "reasonable substitute".

What's wrong with the typical discharge tubes that are often used in physics labs?

Zz.
 
  • #3
Cost. simplicity of implementation. Ease of use. There are probably some HV discharge lamps out there with a closely spaced and intense pair of lines in the VIS regions separated by less than a few nm. I have used deuterium and mercury for single lines.
I don't quite grasp the coherence length for non-laser source but I do know the sodium worked well here. Not sure of the others.

fs
 
  • #4
fsonnichsen said:
Cost. simplicity of implementation. Ease of use.

Er... yeah, they're not that expensive. They are simple to use. And you flick a switch, it glows! How much more "ease of use" than that?

There are probably some HV discharge lamps out there with a closely spaced and intense pair of lines in the VIS regions separated by less than a few nm. I have used deuterium and mercury for single lines.

I have no idea what you are talking about here. What "lines"? If these are the spectral lines, the line separation depends on the resolution of your instrument! I mean, if I want the lines to be more separated, I can crudely use a diffraction grating with more lines/mm. There, larger separation.

Zz.
 
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  • #5
By sodium lines I mean the pair of lines at 588.9950 and 589.5924 . (Yep-i always have to look that up!)
That is a great spacing because it is only 0.5nm----a good test for a spectrometer and they are intense, isolated from other lines, and nearly equal in height.

I am working with a "heterodyne spatial" spectrometer design--basically a form or interferometer---and the bandwidth is very narrow but the optical throughput is comparatively high and one--apparently-can get great resolution.

So I am seeking an intense pair of VIS lines at such a spacing for my source. And-drat--the source needs to be quazi-coherent. :frown: I am guessing a few mm.

I don't really want to get crazy with setting up some type of emission experiment for the lines--just want a reliable source so I can spend my time worrying about the spectrometer design. (feel like I am acting spoiled here ).:smile: Unfortunately I don't usually think much about sources-until now. Of course that is the fun of it. Amazing the important things that never appear in the textbooks.

thanks
fritz
 
  • #6
ZapperZ said:
Er... yeah, they're not that expensive. They are simple to use. And you flick a switch, it glows! How much more "ease of use" than that?

I don't think you are going to find anything cheaper and easier to use.
 
  • #7
fsonnichsen said:
By sodium lines I mean the pair of lines at 588.9950 and 589.5924 . (Yep-i always have to look that up!)
That is a great spacing because it is only 0.5nm----a good test for a spectrometer and they are intense, isolated from other lines, and nearly equal in height.
I am working with a "heterodyne spatial" spectrometer design--basically a form or interferometer---and the bandwidth is very narrow but the optical throughput is comparatively high and one--apparently-can get great resolution.
So I am seeking an intense pair of VIS lines at such a spacing for my source. And-drat--the source needs to be quazi-coherent. :frown: I am guessing a few mm.
I don't really want to get crazy with setting up some type of emission experiment for the lines--just want a reliable source so I can spend my time worrying about the spectrometer design. (feel like I am acting spoiled here ).:smile: Unfortunately I don't usually think much about sources-until now. Of course that is the fun of it. Amazing the important things that never appear in the textbooks.

thanks
fritz

Not sure why you can't just switch to a high-pressure Sodium lamp, but Hg I spectra also has a doublet candidate around 579 nm. Neon also has a lot of closely spaced lines in the region you are interested in (https://physics.nist.gov/cgi-bin/AS...=on&enrg_out=on&J_out=on&submit=Retrieve+Data).

Short arc sources are in general reasonably spatially coherent, but if you have special requirements you will probably have to spatial filter the source beam.
 
  • #8
Andy
I think the high pressure lamps have a lot of Lorentz broadening. However I was able to locate a Ne lamp this weekend and will try it today. There are a couple of intense lines around 533nm.
I have not worked with arc sources but your comment on the coherency is interesting--I will read up on them.
Thanks!
Fritz
 
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  • #10
Yes-their spectra for the Ne lamp shows peaks starting at 533.06.
I assume it has a reasonable coherency given that it is a gas lamp.

I guess the Na lamp is history save for a few bulbs left in old inventory.

Thanks
fritz
 

1. What is a sodium vapor lamp and how does it work?

A sodium vapor lamp is a type of gas-discharge lamp that produces light by passing an electric current through a tube filled with sodium vapor. The vapor is excited by the electrical current, causing it to emit a yellow-orange light. This light is then used for spectral calibration and diffraction work.

2. Why are sodium vapor lamps used for spectral calibration and diffraction work?

Sodium vapor lamps emit a very specific wavelength of light (589.3 nanometers), making them ideal for use in spectral calibration and diffraction work. This wavelength is commonly used as a reference point in spectroscopy and other scientific measurements.

3. What is the difference between low pressure and high pressure sodium vapor lamps?

The main difference between low pressure and high pressure sodium vapor lamps is the pressure of the sodium vapor inside the lamp. Low pressure lamps have a lower pressure, which results in a more narrow and specific emission of light, making them better for spectral calibration and diffraction work. High pressure lamps have a higher pressure, resulting in a broader emission of light that is better suited for general lighting purposes.

4. How are sodium vapor lamps used for diffraction work?

In diffraction work, sodium vapor lamps are used as a source of monochromatic light, meaning light of a single wavelength. This light is then directed through a diffraction grating, which separates the light into its component wavelengths. This allows for the analysis of the sample being studied, as the diffraction pattern produced will be unique to the sample's molecular structure.

5. What are the benefits of using sodium vapor lamps for spectral calibration and diffraction work?

Sodium vapor lamps have several benefits for spectral calibration and diffraction work. They have a long lifespan, are relatively low cost, and produce a consistent and specific wavelength of light. They are also easy to operate and maintain, making them a popular choice for scientific research and analysis. Additionally, the use of sodium vapor lamps allows for accurate and precise measurements, making them an essential tool in many scientific fields.

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