Spectrum of Doubly Ionised Iodine

Abstract

THIS spectrum has been under investigation for some time past in the visible and ultra-violet regions, and it has been found that a good many of the strong lines owe their origin to the terms of 2O₂P₁, 2O₂P₂, and 2O₂P₃ electronic configurations. All the quartet terms for these have been recognised, the lines originating from them having been obtained by a consideration of the spectra of doubly ionised indium, tin, and antimony which have been elucidated by various investigators. In spite of the difficulties of correctly estimating the intensities of lines for highly ionised elements, the multiplets in the present case follow the usual intensity rules fairly well. The 2O₂(P₁←P₂) and 2O₂(P₂←P₃) lines are grouped about the region λλ 3900 A. and 3100 A. respectively. The following table gives the separations which occur between the components of a few of the principal multiple terms. For the purpose of comparison, the corresponding separations in the analogous spectra of doubly ionised fluorine, chlorine, and bromine (already determined by previous investigators) have also been included in the table.