Why are the spectral lines weak in my hydrogen Geissler tube?

In summary, the conversation discusses the use of a hand spectroscope to examine the spectrum of two geissler tubes, one containing helium and the other containing hydrogen. While the helium spectrum shows expected results, the hydrogen spectrum is disappointing and appears to have a background of broad-spectrum light. The cause of this is uncertain, but it could be due to scattering of light or damage to the spectroscope. The conversation also mentions a website that compares different types of geissler tubes and notes that the spurious emissions in the spectrum could be the cause of the background in the hydrogen tube. The conversation also considers the possibility that the voltage or pressure may be favoring molecular emissions over atomic emissions. Additionally, there is a discussion about the possibility
  • #1
Orthoceras
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TL;DR Summary
Why are the spectral lines weak in the light from my hydrogen geissler tube, compared to the continuous background? What is the source of this continuous background?
Using a hand spectroscope, I looked at the spectrum of two geissler tubes, helium and hydrogen. The helium spectrum is what I expected, dominated by five distinct lines. The hydrogen spectrum, however, is somewhat disappointing. It is dominated by an almost continuous spectrum, it is not evident where the H-α, H-β, H-γ lines are. Is this normal for a hydrogen geissler tube? Is it because hydrogen is composed of molecules instead of atoms?

spectrum He.png
spectrum H2.png
 
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  • #2
Orthoceras said:
Is this normal for a hydrogen geissler tube? Is it because hydrogen is composed of molecules instead of atoms?
My best guess is that the spectrum is normal for molecular hydrogen, but I can't say why you also have a background of broad-spectrum light. Perhaps it is scattering of the light from the spectral lines from the spectroscope? Even you helium spectrogram is showing significant 'scattered' light from its handful of strong spectral lines. Is your spectroscope clean and free of damage on its grating/prism and other clear pieces that the light travels through?
 
  • #3
A website selling geissler tubes compares their "new style geissler tube" to the "old style tubes". It says the old style tubes are inferior because "spurious emissions in the spectrum are of considerable number and intensity". Unfortunately, the website does not specify the cause of the spurious emissions. The spurious emissions look like the background in my hydrogen tube. However, at the same time I am starting to doubt the H-α is really present in my tube. I guess my tube has been damaged somehow, and doesn't behave like a hydrogen tube anymore.

old and new style geissler tubes klad.png
 
  • #4
Orthoceras said:
However, at the same time I am starting to doubt the H-α is really present in my tube. I guess my tube has been damaged somehow, and doesn't behave like a hydrogen tube anymore.
What is the voltage of your tube? Note that H-alpha is an atomic transition, not a molecular one. The hydrogen in your tube has to be split apart and then excited if you want to see the alpha, beta, and gamma spectral lines of atomic hydrogen. It might be that a difference in voltage or pressure favors molecular emissions over atomic emissions.

Also, I think you have the new-style and old-style spectra reversed. The new style, according to the link, has greatly reduced 'spurious' emissions, and should be the first image.
 
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  • #5
I used a cheap high voltage generator from ebay. When connected to the Geissler tube, it produces 5 kV pulses, and each pulse results in a discharge through the gas, at 60 mA during 2 μs. Maybe a traditional Ruhmkorff coil generator would produce a higher current and another pulse duration.

You are right, I accidentally reversed the new/old labels"
 
  • #6
Well, I'm afraid that I can't help you any further, as I'm not familiar with these tubes. Best of luck though.
 
  • #7
Thanks
 
  • #8
Maybe the glass fluoresces due to bombardment with particles.
 
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  • #9
tech99 said:
Maybe the glass fluoresces due to bombardment with particles.
Not as far fetched as it sounds.

Many years ago I had access to a 10mW Argon Laser, 488nm Blue emission.

I was playing with some photographic filters that screw on to the front of a camera lens
.
There were a few UV-block filters (Skylight Filters) included in the mix. The higher-priced ones were fine, two of the bargain-basement cheapy filters glowed Red under the Blue Laser light!

Take-Away: The bargain-basement varieties should stay locked away in the basement.:oldfrown:

Cheers,
Tom
 

1. Why are the spectral lines in my hydrogen Geissler tube weak?

The spectral lines in a hydrogen Geissler tube may appear weak due to several factors. One possible reason is that the tube is not properly excited, resulting in a low intensity of light emitted. Another reason could be that the tube is not filled with enough hydrogen gas, which is necessary for the spectral lines to appear bright and distinct. Additionally, the quality and age of the tube can also affect the intensity of the spectral lines.

2. Can the weak spectral lines in my hydrogen Geissler tube be fixed?

Yes, the weak spectral lines in a hydrogen Geissler tube can be fixed by ensuring that the tube is properly excited and filled with enough hydrogen gas. If the tube is old or damaged, it may need to be replaced in order to produce brighter spectral lines.

3. Are there any other gases that can be used in a Geissler tube to produce stronger spectral lines?

Yes, there are other gases that can be used in a Geissler tube to produce stronger spectral lines. For example, helium and neon are commonly used in Geissler tubes and can produce bright and distinct spectral lines.

4. How do the spectral lines in a hydrogen Geissler tube relate to the energy levels of hydrogen atoms?

The spectral lines in a hydrogen Geissler tube correspond to the energy levels of hydrogen atoms. When the atoms are excited, they emit energy in the form of light, which appears as spectral lines. The specific wavelengths of these lines correspond to the specific energy levels of the hydrogen atoms.

5. Can the intensity of the spectral lines in a hydrogen Geissler tube be adjusted?

Yes, the intensity of the spectral lines in a hydrogen Geissler tube can be adjusted by changing the voltage or current applied to the tube. This affects the level of excitation of the hydrogen atoms and therefore, the intensity of the emitted light. Additionally, using a spectroscope can help to filter out unwanted light and enhance the visibility of the spectral lines.

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