Measuring the Helium Spectrum: Friederich Paschen 1916

In summary, this page contains measurements of the fine structure of singly ionized helium at +- 4686 Angstrom. The three most likely transitions that are being measured are the 3d 5/2 to 4f 7/2 transition, the Ia, IIc transition at 4685.803 Angstrom, and the transition between levels 6 and 12. However, no measurements of the lines mentioned by Bohr have been found.
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neilparker62
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Need help interpreting measurement.
Re page 14 of following reference:

https://zenodo.org/record/1447321#.XSyx3z9LjIU
If I understand correctly this page is showing a set of measurements for the fine structure of singly ionized Helium at +- 4686 Angstrom. Can we figure out from this which specific transitions are being measured ? In particular I'm interested in establishing which represents the 3d 5/2 to 4f 7/2 transition. I think it's most likely the one labelled Ia, IIc at 4685.803 A.

Alternatively if there's another source of measured (not calculated!) values for this fine structure complex, please point me in the right direction. I have hunted high and low but it seems no serious measurement on the Helium Spectrum has been done since Paschen's in 1916 ?!

Or from astronomy experts: are we able to measure stellar spectra accurately enough to resolve the 4686 fine structure ? As well as other of "Bohr's Helium lines" which are generally transitions of He+ from energy levels above 4 to level 4. Paschen has measurements at +- 6560 A, 5411 A, 4859 A, 4541 A, 4338 A, 4199 A and 4100 A showing transitions from levels 6 to 12 (to level 4). Each of these is probably a fine structure "forest" itself but I would guess the readings taken are of the dominant component or perhaps an average of dominant components.
 
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phyzguy said:
Of course there have been more recent measurements. A good place to look is at NIST. The link below shows measurements of the lines you are asking about, and there are links to the references where the data was taken, as well as the energy levels for HeII.

https://physics.nist.gov/PhysRefData/Handbook/Tables/heliumtable2.htm
Many thanks but had already trawled NIST looking for data. If you follow the refs on 4686 lines, all you find is a reference to "unpublished calculations" - not measurements. I even confirmed that via an email to NIST.
 

1. What is the significance of Friederich Paschen's 1916 measurement of the helium spectrum?

Friederich Paschen's measurement of the helium spectrum in 1916 was significant because it provided the first accurate and comprehensive understanding of the spectral lines of helium. This measurement helped to confirm the existence of helium as an element and contributed to the development of atomic theory.

2. How did Friederich Paschen measure the helium spectrum in 1916?

Friederich Paschen used a spectrograph, a device that separates light into its component wavelengths, to measure the helium spectrum. He passed light from a helium gas discharge through a narrow slit and then through a prism to produce a spectrum of distinct lines. He then measured the wavelengths of these lines using a calibrated scale.

3. What is the significance of the wavelengths measured by Friederich Paschen in 1916?

The wavelengths measured by Friederich Paschen in 1916 were significant because they provided the first accurate values for the spectral lines of helium. These wavelengths helped to confirm the existence of helium as an element and contributed to the development of atomic theory.

4. How did Friederich Paschen's measurement of the helium spectrum contribute to our understanding of atomic theory?

Friederich Paschen's measurement of the helium spectrum contributed to our understanding of atomic theory by providing evidence for the existence of helium as an element and by helping to refine our understanding of the structure of the atom. The distinct spectral lines observed in the helium spectrum were later explained by the Bohr model of the atom, which proposed that electrons exist in discrete energy levels.

5. How has Friederich Paschen's measurement of the helium spectrum impacted modern science?

Friederich Paschen's measurement of the helium spectrum has had a lasting impact on modern science. It provided key evidence for the existence of helium as an element and helped to refine our understanding of atomic theory. This measurement also paved the way for further research on the properties and behavior of helium, which has many practical applications in fields such as cryogenics and nuclear energy.

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