Ionization in the Plasma of a Copper Arc

From the relative intensities of arc and spark lines observed in a d-c arc in air between copper electrodes, the degree of ionization of eleven elements added to the copper has been determined. With the aid of Saha’s ionization equation, the electron density in the arc was calculated to be 2.4×1014 cm−3. Partition functions for atoms and ions of 29 elements are newly calculated or estimated and a table of first ionization potentials and partition functions of atoms and ions for seventy elements is presented. The degree of ionization of seventy elements separately added to the arc is calculated. The electron density in the arc is confirmed by three independent spectroscopic and electrical determinations. The data developed in this paper will enable the calculation of relative transition probabilities from the intensities in the NBS Tables of Spectral-Line Intensities.