Absorption Spectrum of Indium Vapour in the Schumann Region

Abstract

THE ground-state of the indium atom is 5s² 5p ²P⁰½ and the term system responsible for the ordinary series spectrum—that is, the system built on the 5s² S₀ ground-state of the ion—was summarized and extended by Paschen¹. Also included in his list are the following three terms: 5s5p^{2 4}P, 5s5p^{2 2}D and 5s5p6s ⁴P. Of these, the first-named was originally identified by Sawyer and Lang² and by Lansing³ independently, and seems well established; the other two terms are much more tentative. The sp²-configuration should give other, hitherto unidentified terms, ²S and ²P, remembering that the use of Russell-Saunders symbols is merely conventional, as we are dealing with a case which probably departs markedly from LS-coupling. Rough estimates indicate that these terms, and those of other configurations in which two electrons are excited, will lie above the normal ionization potential.