Regularities in the Third Spectrum of Thorium

Abstract

The thorium spectrum is very rich in lines and extends into the far ultraviolet beyond 200A. The lines have been classified into II, III and IV as far as 1500A by means of the pole effect. A condensed spark in air and in nitrogen between metallic electrodes was used. The Th III spectrum lies on the short side of 3500A with most of its strong lines between 3000 and 2200A. Twenty-four energy levels are given.