The Arc Spectrum of Osmium

Over 1050 osmium lines have been classified as transitions between 137 terms of Os I. J values have been assigned to all terms without the aid of Zeeman effect studies. If Hund theory is to apply to Os I then the J assignment is unique. The classification is consistent as regards absorption lines, persistent lines, intensities, and comparison with analogous spectra. Comparison with iron shows that nearly all the terms from d⁶s² and d⁷s found in Fe I have been found in Os I. The normal state of osmium is 5d⁶6s²(⁵D₄). The order of $J=2$ and $J=3$ is inverted in the four lowest "multiplets." Electron configurations and "multiplets" overlap to such an extent that the unambiguous assignments of L and S values and electron configurations are impossible for most terms. If the term assumed to be 5d⁶6s(⁶D)7s⁷D₄ is correctly designated, then a simple series calculation gives 8.7 volts as an approximate value for the ionizing potential of osmium. New wave-length measurements to extend the analysis are to be made using a grating having a dispersion of 0.4A/mm in the second order. Evidence is presented to show that the normal electron configuration of iridium is 5d⁷6s².