Abstract
A new light source has been developed which produces numerous self-reversed lines in both the first and second spectra of rare-earth elements. It consists of a pulsed arc discharge with a peak current of 75 amperes and an on-time of one millisecond per cycle. Resonance lines are nearly completely absorbed, and can be distinguished by this character. From spectrograms obtained with this light source, the ground states of Tb I and U II were determined, and those reported for Yb I, Yb II, Tm I, Tm II, and U I were confirmed.