I know helium is the most commonly used gas in the discharge lamps used in UPS, and that you can also use Neon or Argon. But I can't seem to find any information on why helium is the go to choice?
Is it because of the higher photon energy or higher intensity or something else entirely?
Thanks in advance for any responses.
Dear Dr. Fabian Fogarty,
helium gas-discharge lamp is the most used in UPS because of the high ionization energy of helium resulting in a high photon energy (He(I)=21.22 eV and He(II)=40.81 eV) of the emitted radiation which is needed for photoemission. A thin Al foil can also be used to filter any He(I) from the He(II) radiation.
The width of He (I) radiation is sufficiently small that the resolution of the spectrometer is limited by other factors.
On the contrary, the wavelengths produced from discarge lamps containing neon or argon consisting of closely spaced multiplets.
Best regards, Pierluigi Traverso.
For reference, the Ne(I) and Ne(II) lines have energies of 16.8 and 26.9 eV respectively. The Ne linewidths are around 100 meV, much like those of He
Dear Fabian Fogarty
Please refer to the article, “Absorption of Helium and other Gases under the Electric Discharge”.
This article can be found via the following link:
https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1912.0092
He I has the by far narrest linewidth and only few and Low intensityl sattelites. He II is usefull for VB measurements where the HeI sattelte May obskur the VB or Fermi edge. In Addition the discharge tube suffers not as much as by Ar, or Ne discharges. Ne May be usefull if you have an VUV monochromator to select the desired line.
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