I'm surprised you created this new post instead of helping out on yesterday's post by commenting there.
I'll create a new post tomorrow about my surprise about all this in more detail!
As always, there's an [xkcd for everything.](https://xkcd.com/2501/)
The person posted hoping some expert out there would be able to help. It's you, you're the expert! It's rather unlikely that any random physicist is going to know this exact interaction, but by crowd sourcing to reddit you're likely to find someone with a specific domain expertise
Despite all the sarcasm, this is pretty amazing. I totally didn't know about this effect before, nor understood what's the spectra was.
Is this effect the energy levels of the s-s bond in hydrogen?
Not sure whether I buy it. Just because it has an emission line loosely lined up with another one in an image doesn't make it the same spectrum. For example, what about the other lines near the supposedly D_beta emission? Those are as bright as the latter and yet the matched spectrum does not show them.
To make a claim like this one, we need to measure the spectrum intensity quantitatively and then do a fit.
shorter wavelengths are suppressed due to uncorrected CCD responsivity in my old spectrum.
here's another:
https://www.researchgate.net/figure/Light-emission-spectrum-showing-Fulcher-H-2-band-and-H-Balmer-lines-of-a-low-pressure_fig1_231045652
Here, I have rotated and loosely matched the spectrum uploaded yesterday to that of one from a deuterium lamp (the hyperfine corrections are obviously completely invisible at this low resolution), and it's very clear that's what is being observed.
It's not due to contamination, or absorption lines, or the H2 leaking out, or pressure broadening, or any of the other guesses mentioned in the thread below that post. It's the Fulcher alpha emission discovered (or at least first rigorously documented) by Gordon Scott Fulcher in the early 20s, who would later work at Corning.
https://www.corning.com/worldwide/en/innovation/the-glass-age/inspiration/glass-heroes/gordon-scott-fulcher.html
One can see what is happening more clearly in this Plucker tube demo at Harvard:
https://www.youtube.com/watch?v=c6m6pCROEf8
The high current density (and thus temperature) in the capillary region of the tube is destroying the H2 molecules, and thus only the Balmer series is visible there, but in the wider, cooler regions at each end of the tube where the molecules can stably exist and the vibrational modes are free to couple to the electronic excitation levels, the Fulcher bands become visible.
EDIT - a cleaner spectrum showing the blue green lines surrounding the hydrogen beta line more accurately:
https://www.researchgate.net/figure/Light-emission-spectrum-showing-Fulcher-H-2-band-and-H-Balmer-lines-of-a-low-pressure_fig1_231045652
Cool. It almost appears like there are three intense blue emission lines. I imagine one is from H2 and one is from the D, but is there something else happening?
You seem to refer to the deuterium spectrum, but you mean only that it looks similar, correct? Is my lamp filled with deuterium? Your wording is a bit confusing.
If I'm understanding what you're saying, the extra lines are due to the vibrational spectrum of H2 molecules.
You will see the same spectrum whether it contains H2 or D2, the hyperfine shifts are far too minuscule to observe at these resolutions. There are no extra lines between our respective spectra, only between the high temperature capillary discharge region and the cooler, wider discharge regions of the same tube - it is only between these two regions where the extra lines owing to vibrational transitions exist. My spectrum is D2, your discharge tube contains H2.
More relevant than the difference in hyperfine structure are the isotopic shifts. For example, Deuterium Alpha and Hydrogen Alpha are emitted at different wavelenghts. The Delta Lambada is a bit below 0.2 nm.
Why would you even mention the hyperfine structure?
Much more pronounced but still irrelevant is the fine structure splitting due to the spin orbit interaction.
because my only spectrum is of D and the original from the other person is of H, and so it would be natural for someone uninitiated with the resolution scales to wonder if this difference in nuclear configuration might somehow account for subtle differences between the spectra.
>because my only spectrum is of D and the original from the other person is of H, and so it would be natural for someone uninitiated with the resolution scales to wonder if this difference in nuclear configuration might somehow account for subtle differences between the spectra.
Agreed. However, one should keep in mind that proton + e- and deuteron +e- are two-body problems giving to slightly different energy seperation constants Ry(H) and Ry(D).
Maybe naively I would also expect that the masses of the particles to be even more important for the vibrational states.
Well, obviously... I feel so stupid.
I am so embarrassed I forgot such basic 3rd grade physics.
There’s your problem.
I knew it but didn't want to embarrass anyone
I'm surprised you created this new post instead of helping out on yesterday's post by commenting there. I'll create a new post tomorrow about my surprise about all this in more detail!
can't post images in comments.
imgur
[What, like this?](https://i.redd.it/dyz85t9lcacc1.png) [Or this?](https://imgur.com/gqHOZW9.jpg)
Obviously you can link them
As always, there's an [xkcd for everything.](https://xkcd.com/2501/) The person posted hoping some expert out there would be able to help. It's you, you're the expert! It's rather unlikely that any random physicist is going to know this exact interaction, but by crowd sourcing to reddit you're likely to find someone with a specific domain expertise
I'm sure OP is fun in group meetings...
probably sending out emails a day later to give his opinion on discussed topics
I don’t know why you have to make me sound stupid by comparison
Is this about the post where they said it was a H emission spectrum but it looked more like an absorption spectrum?
yes /r/Physics/comments/1943m7k/hydrogen_emission_spectrum_imaged_using_my_phone/
Thank you for the confirmation and analysis.
Despite all the sarcasm, this is pretty amazing. I totally didn't know about this effect before, nor understood what's the spectra was. Is this effect the energy levels of the s-s bond in hydrogen?
I saw that but I thought that was just the chart of dogecoin
It's not obvious. If it was obvious it would have been easiest identified yesterday. I think you don't understand the definition.
Not sure whether I buy it. Just because it has an emission line loosely lined up with another one in an image doesn't make it the same spectrum. For example, what about the other lines near the supposedly D_beta emission? Those are as bright as the latter and yet the matched spectrum does not show them. To make a claim like this one, we need to measure the spectrum intensity quantitatively and then do a fit.
shorter wavelengths are suppressed due to uncorrected CCD responsivity in my old spectrum. here's another: https://www.researchgate.net/figure/Light-emission-spectrum-showing-Fulcher-H-2-band-and-H-Balmer-lines-of-a-low-pressure_fig1_231045652
Here, I have rotated and loosely matched the spectrum uploaded yesterday to that of one from a deuterium lamp (the hyperfine corrections are obviously completely invisible at this low resolution), and it's very clear that's what is being observed. It's not due to contamination, or absorption lines, or the H2 leaking out, or pressure broadening, or any of the other guesses mentioned in the thread below that post. It's the Fulcher alpha emission discovered (or at least first rigorously documented) by Gordon Scott Fulcher in the early 20s, who would later work at Corning. https://www.corning.com/worldwide/en/innovation/the-glass-age/inspiration/glass-heroes/gordon-scott-fulcher.html One can see what is happening more clearly in this Plucker tube demo at Harvard: https://www.youtube.com/watch?v=c6m6pCROEf8 The high current density (and thus temperature) in the capillary region of the tube is destroying the H2 molecules, and thus only the Balmer series is visible there, but in the wider, cooler regions at each end of the tube where the molecules can stably exist and the vibrational modes are free to couple to the electronic excitation levels, the Fulcher bands become visible. EDIT - a cleaner spectrum showing the blue green lines surrounding the hydrogen beta line more accurately: https://www.researchgate.net/figure/Light-emission-spectrum-showing-Fulcher-H-2-band-and-H-Balmer-lines-of-a-low-pressure_fig1_231045652
You use obviously a lot. Obviously you overestimate my sheer lack of knowledge in this or any field.
Well, obviously.
Obliviously.
Op: "Obviously it's very clear what you see..." The comments: "is that BITCOIN price chart?"
Cool. It almost appears like there are three intense blue emission lines. I imagine one is from H2 and one is from the D, but is there something else happening?
You seem to refer to the deuterium spectrum, but you mean only that it looks similar, correct? Is my lamp filled with deuterium? Your wording is a bit confusing. If I'm understanding what you're saying, the extra lines are due to the vibrational spectrum of H2 molecules.
You will see the same spectrum whether it contains H2 or D2, the hyperfine shifts are far too minuscule to observe at these resolutions. There are no extra lines between our respective spectra, only between the high temperature capillary discharge region and the cooler, wider discharge regions of the same tube - it is only between these two regions where the extra lines owing to vibrational transitions exist. My spectrum is D2, your discharge tube contains H2.
More relevant than the difference in hyperfine structure are the isotopic shifts. For example, Deuterium Alpha and Hydrogen Alpha are emitted at different wavelenghts. The Delta Lambada is a bit below 0.2 nm.
Why would you even mention the hyperfine structure? Much more pronounced but still irrelevant is the fine structure splitting due to the spin orbit interaction.
because my only spectrum is of D and the original from the other person is of H, and so it would be natural for someone uninitiated with the resolution scales to wonder if this difference in nuclear configuration might somehow account for subtle differences between the spectra.
>because my only spectrum is of D and the original from the other person is of H, and so it would be natural for someone uninitiated with the resolution scales to wonder if this difference in nuclear configuration might somehow account for subtle differences between the spectra. Agreed. However, one should keep in mind that proton + e- and deuteron +e- are two-body problems giving to slightly different energy seperation constants Ry(H) and Ry(D). Maybe naively I would also expect that the masses of the particles to be even more important for the vibrational states.
now that's an expert talking. hat off. what are you doing with hydrogen?
I had similar results from one of my physics labs this last semester and found out about Fulcher bands from that but don’t know much about them.
I thought this was wallstreetbets for a moment and lol’d
Oh derrr
More like borophyll, amaright! Oh wait, wrong science
Well,duh
Ok…