The Arc Spectrum of Cobalt

The present analysis classifies 2725 lines and identifies 768 multiplets of the doublet, quartet, and sextet systems. The results are in complete agreement with Hund's theory, and indicate that all the important features of the structure of the neutral atom are now known. The results agree closely with those of Catalan and Antunes (who classified 2076 lines) except where changes in term-designations have been made on account of Zeeman data or of a new interpretation of the convergence of the components of multiple terms to their limits. The principal ionization potential is 7.84 volts. Tables are given of terms, electron configurations, and of 3007 lines, of which 91 percent are classified. Zeeman effects have been observed for 871 lines and $g$ values derived for 270 levels. The large majority of these have nearly the theoretical values for $\mathrm{LS}$ coupling. There are some cases of $g$ sharing (Table VII). The wave-length list includes measures of 1282 lines made with the interferometer by Dr. Keivin Burns of the Allegheny Observatory, which, by his generosity, are here published for the first time; and also 274 newly measured lines between $\lambda 2230$ and $\lambda 1814$.