The Arc Spectrum of Nickel (Ni I)

Extension of the analysis of the spectrum of Ni I.---Almost all the known lines (1071) of Ni I have been classified. There are included in the classification 66 lines from the solar spectrum which have not been found in the laboratory. The spectrum, in spite of its apparent complexity, is admirably regular. Every observed term fits without constraint into the scheme predicted by Hund's theory. A few of the predicted terms have not been found, but in all cases their combinations should either be faint or out of range. Term values, combinations, configurations and identified lines are tabulated.Ionization potential of the Ni atom.---The principal ionization potential of the neutral Ni atom is calculated to be 7.606 volts. It corresponds to a double electron change from the configuration d⁸s² to d⁹.