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I'm interested in the spectra of gas discharge tubes. Taking neon as an example, when I look up on NIST the spectra for neon, I find excitation states up to Ne IX. Where do I find/how do I work out which excitation states are predominate in a neon light? Is it voltage- or current-dependent, or depending on transition probabilities somehow? For context, I studied physics but lack some of the finer details that chemists have when it comes to electron configurations.

Ideally I'd like an answer that applies to elements other than neon, as all of the noble gases and a couple of others are common inside gas discharge tubes.

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  • $\begingroup$ It is a good question but horribly difficult. I have asked plenty of spectroscopists (online) and via email about line assignments but did not get any useful reply $\endgroup$
    – AChem
    Nov 18, 2020 at 16:41
  • $\begingroup$ The lines are narrow and the frequencies specific to particular excitations. Match the observed frequencies from the discharge tube to the known transitions and you have the answer. $\endgroup$
    – matt_black
    Nov 18, 2020 at 16:44
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    $\begingroup$ At least if the gas is low pressure. High pressure tubes have much broader lines but most simple display tubes are low pressure. And don't forget most also contain not just the pure gas but also some other components. $\endgroup$
    – matt_black
    Nov 18, 2020 at 16:46
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    $\begingroup$ A @matt_black, states, pressure is an influence. Some spectral lines in aurorae could not be reproduced on earth until high-vacuum technology became available. If the mean free path of the atom is short, some excited states may not have a chance to radiate before a collision. As for higher states, and higher level of ionization, an electron beam or high-energy photons may be needed, rather than a glow discharge. $\endgroup$ Nov 19, 2020 at 0:00
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    $\begingroup$ @matt-black, once I have this sorted I do plan to use spectra of common penning mixtures (ie doping neon with argon) and mix in some of the doping elements' spectra. I am also unfortunately going from the theoretical into the observed side here, ie I want to create the RGB values out of spectra to match the chemistry of the gases inside rather than to match an observed tube (allowing me to generate light colours based on their gas composition once I load up the different spectra). $\endgroup$
    – Beanman
    Nov 19, 2020 at 9:38

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