IX. The vacuum spark spectra of some the heavier elements, and series classification in the spectra of ionised atoms homologous with copper, silver, and gold

Abstract

§ 1. The vacuum spark spectra of the lighter elements have furnished, in the hands of Millikan and Bowen, data for a remarkable extension of the field of optical series spectra. Their recognition and discussion of the sequence of doublet spectra of ionised atoms similar to lithium and sodium has emphasized certain difficulties in the interpretation of doublet separations which we shall mention briefly in § 4. The writer has, by means of spectra photographed by him in Prof. Millikan’s laboratory at the California Institute of Technology and in the laboratory of the Mount Wilson Observatory, essayed the extension of this work into the field of elements lying in the middle part of the periodic table.