An investigation of extreme ultra-violet spectra, with a vacuum-grating spectrograph

Abstract

It has been pointed out in another communication* that some considera­tions connected with the investigation of ionisation potentials for the different elements made it necessary to work out their series spectra as far down in the ultra-violet as it was practicable to go. The results of some studies with quartz and fluorite spectrographs have already been published, and in the present communication an account is given of some preliminary observations made with a vacuum-grating spectrograph. This work, as well as that in other directions, has had to be discontinued for the present through the exigencies of the war situation/and is therefore incomplete. The results obtained so far, however, are interesting in that they show that it is quite feasible to investigate, with comparative ease, spectra including wave-lengths as short as λ = 584 Å. U. II. The Vacuum-grating Spectrograph . The vacuum-grating spectrograph was designed by and obtained from the Adam Hilger Company. A sectional plan and sectional elevation of this instrument is shown in fig. 1. Sketches of the grating mounting are shown in fig. 2, and others of the slits, slit taps, auto-collimating eyepiece and film carrying taps are sketched in fig. 3.