The Arc Spectrum of Platinum

Eight new levels and forty-four new combinations have been found in Pt I. Fifty-six new lines have been measured in the ultra-violet. An examination of the Zeeman effect and the subsequent determination of the g-values for most of the terms has permitted a reasonable interpretation of many levels. Low structures are d⁹s, d⁸s² and d¹⁰; middle terms arise from d⁹p and d⁸sp; high configurations are d⁹·s, d⁸s·s, with an indication of d⁸s·d. Quintet terms appear in the middle and high sets. From the failure of the intensity and interval rules and the irregularity of the g-values, it is evident that the Russell-Saunders coupling has almost completely broken down, as is to be expected from the position of platinum in the periodic table. There is only an approximate similarity with the theoretically analogous spectrum of Ni I. Ionization potentials are approximately calculated as 8.9 volts for d⁹s to d⁹ and 9.7 volts for d⁹s to d⁸s.