The Disappearing Gap in the Spectrum

Abstract

II. TURNING to Fig. 1, B, which is repeated here for convenience of reference, this shows the various outposts where from time to time spectral lines have been located. It will be seen that there is still a considerable gap between 16.35, tne limit obtained with the vacuum grating at the L series of aluminium, and 17.39, tne limit with the crystal spectrometer at the L series of zinc. Between these limits no spectral lines are known, but there is evidence of the excitation of such lines, and data have been obtained for the high-frequency limits of spectra in this region.