Recent improvements in rare gas continua in the vacuum ultraviolet region

Abstract

It has been observed that a d.c. condensed, self-triggered discharge of helium at high pressures (up to 800 mm Hg) produces a strong continuous emission spectrum in the 1050–4000 Å region, with a broad intensity maximum around 2500 Å. This continuum is much stronger than the other continuum of helium in the 600–1000 Å region and has comparable intensity with the hydrogen continuum. In the same discharge, the resonance series lines beginning at 584 Å were very much broadened on both sides of the center; and, in addition, quite a few diffuse bands appeared in the regions between successive lines of the series. Consequently, the spectrum in the 500–600 Å region appeared as a continuum crossed by broad absorption lines of the resonance series. Similar evidence was also observed in other rare gases, particularly in Xe and A. Experimental conditions and speculation about the origin of the continuum mentioned above will be presented.With some minor modifications in the method of excitation, the Hopfield continuum of helium (600–1000 Å) was greatly intensified and stabilized. It can be used for absorption measurements not only with the photographic method but also with the photoelectric method. Experimental conditions for the source and several examples of absorption measurements using this continuum with the photoelectric method will be presented.Existence of two intensity maxima in this helium continuum (600–1000 Å) was reconfirmed. However, by changing the excitation conditions, the maximum at the shorter wavelength side disappeared, while the other remained relatively unchanged in appearance. The simultaneous study of the helium bands in the visible and ultraviolet regions in conjunction with the continuum confirmed the previous suggestion concerning the origin of the continuum.