The effect of argon on certain spectra

It has been shown in several papers of recent years that the admixture of the inactive gases with substances emitting spectra results in certain cases in profound modification of these spectra. In some cases this is in the form of a redistribution of spectral intensity, but in other cases the isolation of entirely new spectra is effected. Remarkable results of this kind have been found by Merton, working with helium. These include a redistribution of intensity in the secondary spectrum of hydrogen (which has been partially co-ordinated with other physical effects), and under other conditions a peculiar facility in isolating the higher members of the Balmer Series. In connection with carbon, helium favours the production of certain spectra appropriate to extremely low pressures, and with other spectra effects an isolation otherwise difficult or impossible. The effect of argon and oxygen on the secondary spectrum of hydrogen has been further investigated by Barratt, while Rayleigh has shown that the inactive gases modify the spectrum of the nitrogen afterglow. By way of introduction, the chief results of these investigators are summarised below. The effect of Helium on the Secondary Spectrum of Hydrogen. This was observed in tubes containing high pressure helium and a little hydrogen, and consists in a modification of the intensities of certain classes of lines. Certain lines showed marked enhancement (some new lines were also produced), other lines remained unaffected, and a third class had their intensity reduced. A general correlation of these modifying influences seemed to show that: (1) In the red and yellow in particular, lines which were favoured by high pressure showed a Zeeman effect; most were also favoured by large current density and by the condensed discharge, and usually were enhanced by helium. (2) Fulcher bands, produced by cathode rays of low energy, were weakened by increasing current density and by the condensed discharge, and were not usually enhanced by helium. (3) The Stark effect is unrelated to other classifications.