Emission Spectra of the Doubly and Triply Ionized Rare Earths*

Abstract

The spectral of the rare earths have been photographed under controlled excitation so that either the spectra of the doubly or triply ionized elements are brought out with maximum intensity. A mild excitation is used in addition to give the first and second spectra for comparison. Some regularities are immediately apparent and vary very gradually through the rare-earth group. The general features of the spectra are discussed in this paper.